diff --git a/health/aidl/default/Android.bp b/health/aidl/default/Android.bp
new file mode 100644
index 0000000..cb78e77
--- /dev/null
+++ b/health/aidl/default/Android.bp
@@ -0,0 +1,76 @@
+// Copyright (C) 2021 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+cc_defaults {
+    name: "libhealth_aidl_common_defaults",
+    vendor: true,
+    shared_libs: [
+        "libbase",
+        "libbinder_ndk",
+        "libcutils",
+        "liblog",
+        "libutils",
+        "android.hardware.health-V1-ndk",
+
+        // TODO(b/177269435): remove when BatteryMonitor works with AIDL HealthInfo.
+        "libhidlbase",
+    ],
+    static_libs: [
+        "libbatterymonitor",
+        "libhealthloop",
+
+        // TODO(b/177269435): remove when BatteryMonitor works with AIDL HealthInfo.
+        "android.hardware.health-translate-ndk",
+    ],
+}
+
+// AIDL version of libhealth2impl.
+// A helper library for health HAL implementation.
+// HAL implementations can link to this library and extend the Health class.
+cc_library_static {
+    name: "libhealth_aidl_impl",
+    defaults: [
+        "libhealth_aidl_common_defaults",
+    ],
+    export_include_dirs: ["include"],
+    export_static_lib_headers: [
+        "libbatterymonitor",
+    ],
+    srcs: [
+        "health-convert.cpp",
+        "HalHealthLoop.cpp",
+        "Health.cpp",
+        "LinkedCallback.cpp",
+    ],
+    visibility: [
+        ":__subpackages__",
+        "//hardware/interfaces/tests/extension/health:__subpackages__",
+    ],
+}
+
+// AIDL version of android.hardware.health@2.1-service.
+// Default binder service of the health HAL.
+cc_binary {
+    name: "android.hardware.health-service.example",
+    relative_install_path: "hw",
+    init_rc: ["android.hardware.health-service.example.rc"],
+    vintf_fragments: ["android.hardware.health-service.example.xml"],
+    defaults: [
+        "libhealth_aidl_common_defaults",
+    ],
+    static_libs: [
+        "libhealth_aidl_impl",
+    ],
+    srcs: ["main.cpp"],
+}
diff --git a/health/aidl/default/HalHealthLoop.cpp b/health/aidl/default/HalHealthLoop.cpp
new file mode 100644
index 0000000..c9a081e
--- /dev/null
+++ b/health/aidl/default/HalHealthLoop.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <health-impl/HalHealthLoop.h>
+
+#include <android-base/logging.h>
+
+#include <health-impl/Health.h>
+#include "health-convert.h"
+
+namespace aidl::android::hardware::health {
+
+// Unlike the HIDL version android::hardware::health::V2_1::implementation::HalHealthLoop,
+// do not define HalHealthLoop::Init because we no longer have Health::getHealthConfig.
+// Let the Health class handle Init.
+void HalHealthLoop::Init(struct healthd_config* config) {
+    callback_->OnInit(this, config);
+}
+
+void HalHealthLoop::Heartbeat() {
+    callback_->OnHeartbeat();
+}
+
+void HalHealthLoop::ScheduleBatteryUpdate() {
+    // ignore errors. impl may not be able to handle any callbacks, so
+    // update() may return errors.
+    if (auto res = service_->update(); !res.isOk()) {
+        LOG(WARNING) << "update() on the health HAL implementation failed with "
+                     << res.getDescription();
+    }
+
+    HealthInfo health_info;
+    auto res = service_->getHealthInfo(&health_info);
+    CHECK(res.isOk()) << "getHealthInfo() on the health HAL implementation failed with "
+                      << res.getDescription();
+    OnHealthInfoChanged(health_info);
+}
+
+int HalHealthLoop::PrepareToWait() {
+    return callback_->OnPrepareToWait();
+}
+
+void HalHealthLoop::OnHealthInfoChanged(const HealthInfo& health_info) {
+    callback_->OnHealthInfoChanged(health_info);
+    set_charger_online(health_info);
+    AdjustWakealarmPeriods(charger_online());
+}
+
+void HalHealthLoop::set_charger_online(const HealthInfo& health_info) {
+    charger_online_ = health_info.chargerAcOnline || health_info.chargerUsbOnline ||
+                      health_info.chargerWirelessOnline;
+}
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/Health.cpp b/health/aidl/default/Health.cpp
new file mode 100644
index 0000000..2d91ce0
--- /dev/null
+++ b/health/aidl/default/Health.cpp
@@ -0,0 +1,341 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "health-impl/Health.h"
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android/binder_manager.h>
+#include <android/binder_process.h>
+#include <android/hardware/health/translate-ndk.h>
+#include <health/utils.h>
+
+#include "LinkedCallback.h"
+#include "health-convert.h"
+
+using std::string_literals::operator""s;
+
+namespace aidl::android::hardware::health {
+
+namespace {
+// Wrap LinkedCallback::OnCallbackDied() into a void(void*).
+void OnCallbackDiedWrapped(void* cookie) {
+    LinkedCallback* linked = reinterpret_cast<LinkedCallback*>(cookie);
+    linked->OnCallbackDied();
+}
+}  // namespace
+
+/*
+// If you need to call healthd_board_init, construct the Health instance with
+// the healthd_config after calling healthd_board_init:
+class MyHealth : public Health {
+  protected:
+    MyHealth() : Health(CreateConfig()) {}
+  private:
+    static std::unique_ptr<healthd_config> CreateConfig() {
+      auto config = std::make_unique<healthd_config>();
+      ::android::hardware::health::InitHealthdConfig(config.get());
+      healthd_board_init(config.get());
+      return std::move(config);
+    }
+};
+*/
+Health::Health(std::string_view instance_name, std::unique_ptr<struct healthd_config>&& config)
+    : instance_name_(instance_name),
+      healthd_config_(std::move(config)),
+      death_recipient_(AIBinder_DeathRecipient_new(&OnCallbackDiedWrapped)) {
+    battery_monitor_.init(healthd_config_.get());
+}
+
+//
+// Getters.
+//
+
+template <typename T>
+static ndk::ScopedAStatus GetProperty(::android::BatteryMonitor* monitor, int id, T defaultValue,
+                                      T* out) {
+    *out = defaultValue;
+    struct ::android::BatteryProperty prop;
+    ::android::status_t err = monitor->getProperty(static_cast<int>(id), &prop);
+    if (err == ::android::OK) {
+        *out = static_cast<T>(prop.valueInt64);
+    } else {
+        LOG(DEBUG) << "getProperty(" << id << ")"
+                   << " fails: (" << err << ") " << ::android::statusToString(err);
+    }
+
+    switch (err) {
+        case ::android::OK:
+            return ndk::ScopedAStatus::ok();
+        case ::android::NAME_NOT_FOUND:
+            return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+        default:
+            return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                    IHealth::STATUS_UNKNOWN, ::android::statusToString(err).c_str());
+    }
+}
+
+ndk::ScopedAStatus Health::getChargeCounterUah(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CHARGE_COUNTER, 0, out);
+}
+
+ndk::ScopedAStatus Health::getCurrentNowMicroamps(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CURRENT_NOW, 0, out);
+}
+
+ndk::ScopedAStatus Health::getCurrentAverageMicroamps(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CURRENT_AVG, 0, out);
+}
+
+ndk::ScopedAStatus Health::getCapacity(int32_t* out) {
+    return GetProperty<int32_t>(&battery_monitor_, ::android::BATTERY_PROP_CAPACITY, 0, out);
+}
+
+ndk::ScopedAStatus Health::getEnergyCounterNwh(int64_t* out) {
+    return GetProperty<int64_t>(&battery_monitor_, ::android::BATTERY_PROP_ENERGY_COUNTER, 0, out);
+}
+
+ndk::ScopedAStatus Health::getChargeStatus(BatteryStatus* out) {
+    return GetProperty(&battery_monitor_, ::android::BATTERY_PROP_BATTERY_STATUS,
+                       BatteryStatus::UNKNOWN, out);
+}
+
+ndk::ScopedAStatus Health::getDiskStats(std::vector<DiskStats>*) {
+    // This implementation does not support DiskStats. An implementation may extend this
+    // class and override this function to support disk stats.
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+ndk::ScopedAStatus Health::getStorageInfo(std::vector<StorageInfo>*) {
+    // This implementation does not support StorageInfo. An implementation may extend this
+    // class and override this function to support storage info.
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+ndk::ScopedAStatus Health::getHealthInfo(HealthInfo* out) {
+    battery_monitor_.updateValues();
+
+    // TODO(b/177269435): BatteryMonitor should store AIDL HealthInfo instead.
+    auto health_info_2_1 = battery_monitor_.getHealthInfo_2_1();
+    if (!::android::h2a::translate(health_info_2_1, out)) {
+        return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                IHealth::STATUS_UNKNOWN, "Cannot translate HIDL HealthInfo to AIDL");
+    }
+
+    // Fill in storage infos; these aren't retrieved by BatteryMonitor.
+    if (auto res = getStorageInfo(&out->storageInfos); !res.isOk()) {
+        if (res.getServiceSpecificError() == 0 &&
+            res.getExceptionCode() != EX_UNSUPPORTED_OPERATION) {
+            return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                    IHealth::STATUS_UNKNOWN,
+                    ("getStorageInfo fails: " + res.getDescription()).c_str());
+        }
+        LOG(DEBUG) << "getHealthInfo: getStorageInfo fails with service-specific error, clearing: "
+                   << res.getDescription();
+        out->storageInfos = {};
+    }
+    if (auto res = getDiskStats(&out->diskStats); !res.isOk()) {
+        if (res.getServiceSpecificError() == 0 &&
+            res.getExceptionCode() != EX_UNSUPPORTED_OPERATION) {
+            return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                    IHealth::STATUS_UNKNOWN,
+                    ("getDiskStats fails: " + res.getDescription()).c_str());
+        }
+        LOG(DEBUG) << "getHealthInfo: getDiskStats fails with service-specific error, clearing: "
+                   << res.getDescription();
+        out->diskStats = {};
+    }
+
+    // A subclass may want to update health info struct before returning it.
+    UpdateHealthInfo(out);
+
+    return ndk::ScopedAStatus::ok();
+}
+
+binder_status_t Health::dump(int fd, const char**, uint32_t) {
+    battery_monitor_.dumpState(fd);
+
+    ::android::base::WriteStringToFd("\ngetHealthInfo -> ", fd);
+    HealthInfo health_info;
+    auto res = getHealthInfo(&health_info);
+    if (res.isOk()) {
+        ::android::base::WriteStringToFd(health_info.toString(), fd);
+    } else {
+        ::android::base::WriteStringToFd(res.getDescription(), fd);
+    }
+
+    fsync(fd);
+    return STATUS_OK;
+}
+
+std::optional<bool> Health::ShouldKeepScreenOn() {
+    if (!healthd_config_->screen_on) {
+        return std::nullopt;
+    }
+
+    HealthInfo health_info;
+    auto res = getHealthInfo(&health_info);
+    if (!res.isOk()) {
+        return std::nullopt;
+    }
+
+    ::android::BatteryProperties props = {};
+    convert(health_info, &props);
+    return healthd_config_->screen_on(&props);
+}
+
+namespace {
+bool IsDeadObjectLogged(const ndk::ScopedAStatus& ret) {
+    if (ret.isOk()) return false;
+    if (ret.getStatus() == ::STATUS_DEAD_OBJECT) return true;
+    LOG(ERROR) << "Cannot call healthInfoChanged on callback: " << ret.getDescription();
+    return false;
+}
+}  // namespace
+
+//
+// Subclass helpers / overrides
+//
+
+void Health::UpdateHealthInfo(HealthInfo* /* health_info */) {
+    /*
+        // Sample code for a subclass to implement this:
+        // If you need to modify values (e.g. batteryChargeTimeToFullNowSeconds), do it here.
+        health_info->batteryChargeTimeToFullNowSeconds = calculate_charge_time_seconds();
+
+        // If you need to call healthd_board_battery_update, modify its signature
+        // and implementation to operate on HealthInfo directly, then call:
+        healthd_board_battery_update(health_info);
+    */
+}
+
+//
+// Methods that handle callbacks.
+//
+
+ndk::ScopedAStatus Health::registerCallback(const std::shared_ptr<IHealthInfoCallback>& callback) {
+    if (callback == nullptr) {
+        // For now, this shouldn't happen because argument is not nullable.
+        return ndk::ScopedAStatus::fromExceptionCode(EX_NULL_POINTER);
+    }
+
+    {
+        std::lock_guard<decltype(callbacks_lock_)> lock(callbacks_lock_);
+        callbacks_.emplace_back(LinkedCallback::Make(ref<Health>(), callback));
+        // unlock
+    }
+
+    HealthInfo health_info;
+    if (auto res = getHealthInfo(&health_info); !res.isOk()) {
+        LOG(WARNING) << "Cannot call getHealthInfo: " << res.getDescription();
+        // No health info to send, so return early.
+        return ndk::ScopedAStatus::ok();
+    }
+
+    if (auto res = callback->healthInfoChanged(health_info); IsDeadObjectLogged(res)) {
+        (void)unregisterCallback(callback);
+    }
+    return ndk::ScopedAStatus::ok();
+}
+
+ndk::ScopedAStatus Health::unregisterCallback(
+        const std::shared_ptr<IHealthInfoCallback>& callback) {
+    if (callback == nullptr) {
+        // For now, this shouldn't happen because argument is not nullable.
+        return ndk::ScopedAStatus::fromExceptionCode(EX_NULL_POINTER);
+    }
+
+    std::lock_guard<decltype(callbacks_lock_)> lock(callbacks_lock_);
+
+    auto matches = [callback](const auto& linked) {
+        return linked->callback() == callback;  // compares shared_ptr
+    };
+    auto it = std::remove_if(callbacks_.begin(), callbacks_.end(), matches);
+    bool removed = (it != callbacks_.end());
+    callbacks_.erase(it, callbacks_.end());  // calls unlinkToDeath on deleted callbacks.
+    return removed ? ndk::ScopedAStatus::ok()
+                   : ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+}
+
+// A combination of the HIDL version
+//   android::hardware::health::V2_1::implementation::Health::update() and
+//   android::hardware::health::V2_1::implementation::BinderHealth::update()
+ndk::ScopedAStatus Health::update() {
+    HealthInfo health_info;
+    if (auto res = getHealthInfo(&health_info); !res.isOk()) {
+        LOG(DEBUG) << "Cannot call getHealthInfo for update(): " << res.getDescription();
+        // Propagate service specific errors. If there's none, report unknown error.
+        if (res.getServiceSpecificError() != 0 ||
+            res.getExceptionCode() == EX_UNSUPPORTED_OPERATION) {
+            return res;
+        }
+        return ndk::ScopedAStatus::fromServiceSpecificErrorWithMessage(
+                IHealth::STATUS_UNKNOWN, res.getDescription().c_str());
+    }
+    battery_monitor_.logValues();
+    OnHealthInfoChanged(health_info);
+    return ndk::ScopedAStatus::ok();
+}
+
+void Health::OnHealthInfoChanged(const HealthInfo& health_info) {
+    // Notify all callbacks
+    std::unique_lock<decltype(callbacks_lock_)> lock(callbacks_lock_);
+    // is_dead notifies a callback and return true if it is dead.
+    auto is_dead = [&](const auto& linked) {
+        auto res = linked->callback()->healthInfoChanged(health_info);
+        return IsDeadObjectLogged(res);
+    };
+    auto it = std::remove_if(callbacks_.begin(), callbacks_.end(), is_dead);
+    callbacks_.erase(it, callbacks_.end());  // calls unlinkToDeath on deleted callbacks.
+    lock.unlock();
+
+    // Let HalHealthLoop::OnHealthInfoChanged() adjusts uevent / wakealarm periods
+}
+
+void Health::BinderEvent(uint32_t /*epevents*/) {
+    if (binder_fd_ >= 0) {
+        ABinderProcess_handlePolledCommands();
+    }
+}
+
+void Health::OnInit(HalHealthLoop* hal_health_loop, struct healthd_config* config) {
+    LOG(INFO) << instance_name_ << " instance initializing with healthd_config...";
+
+    // Similar to HIDL's android::hardware::health::V2_1::implementation::HalHealthLoop::Init,
+    // copy configuration parameters to |config| for HealthLoop (e.g. uevent / wake alarm periods)
+    *config = *healthd_config_.get();
+
+    binder_status_t status = ABinderProcess_setupPolling(&binder_fd_);
+
+    if (status == ::STATUS_OK && binder_fd_ >= 0) {
+        std::shared_ptr<Health> thiz = ref<Health>();
+        auto binder_event = [thiz](auto*, uint32_t epevents) { thiz->BinderEvent(epevents); };
+        if (hal_health_loop->RegisterEvent(binder_fd_, binder_event, EVENT_NO_WAKEUP_FD) != 0) {
+            PLOG(ERROR) << instance_name_ << " instance: Register for binder events failed";
+        }
+    }
+
+    std::string health_name = IHealth::descriptor + "/"s + instance_name_;
+    CHECK_EQ(STATUS_OK, AServiceManager_addService(this->asBinder().get(), health_name.c_str()))
+            << instance_name_ << ": Failed to register HAL";
+
+    LOG(INFO) << instance_name_ << ": Hal init done";
+}
+
+// Unlike hwbinder, for binder, there's no need to explicitly call flushCommands()
+// in PrepareToWait(). See b/139697085.
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/LinkedCallback.cpp b/health/aidl/default/LinkedCallback.cpp
new file mode 100644
index 0000000..2985ffe
--- /dev/null
+++ b/health/aidl/default/LinkedCallback.cpp
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/logging.h>
+#include <android/binder_ibinder.h>
+
+#include <health-impl/Health.h>
+#include <utils/Errors.h>
+
+#include "LinkedCallback.h"
+
+namespace aidl::android::hardware::health {
+
+std::unique_ptr<LinkedCallback> LinkedCallback::Make(
+        std::shared_ptr<Health> service, std::shared_ptr<IHealthInfoCallback> callback) {
+    std::unique_ptr<LinkedCallback> ret(new LinkedCallback());
+    binder_status_t linkRet =
+            AIBinder_linkToDeath(callback->asBinder().get(), service->death_recipient_.get(),
+                                 reinterpret_cast<void*>(ret.get()));
+    if (linkRet != ::STATUS_OK) {
+        LOG(WARNING) << __func__ << "Cannot link to death: " << linkRet;
+        return nullptr;
+    }
+    ret->service_ = service;
+    ret->callback_ = std::move(callback);
+    return ret;
+}
+
+LinkedCallback::LinkedCallback() = default;
+
+LinkedCallback::~LinkedCallback() {
+    if (callback_ == nullptr) {
+        return;
+    }
+    auto status =
+            AIBinder_unlinkToDeath(callback_->asBinder().get(), service()->death_recipient_.get(),
+                                   reinterpret_cast<void*>(this));
+    if (status != STATUS_OK && status != STATUS_DEAD_OBJECT) {
+        LOG(WARNING) << __func__ << "Cannot unlink to death: " << ::android::statusToString(status);
+    }
+}
+
+std::shared_ptr<Health> LinkedCallback::service() {
+    auto service_sp = service_.lock();
+    CHECK_NE(nullptr, service_sp);
+    return service_sp;
+}
+
+void LinkedCallback::OnCallbackDied() {
+    service()->unregisterCallback(callback_);
+}
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/LinkedCallback.h b/health/aidl/default/LinkedCallback.h
new file mode 100644
index 0000000..82490a7
--- /dev/null
+++ b/health/aidl/default/LinkedCallback.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <memory>
+
+#include <aidl/android/hardware/health/IHealthInfoCallback.h>
+#include <android-base/macros.h>
+#include <android/binder_auto_utils.h>
+
+#include <health-impl/Health.h>
+
+namespace aidl::android::hardware::health {
+
+// Type of the cookie pointer in linkToDeath.
+// A (Health, IHealthInfoCallback) tuple.
+class LinkedCallback {
+  public:
+    // Automatically linkToDeath upon construction with the returned object as the cookie.
+    // service->death_reciepient() should be from CreateDeathRecipient().
+    // Not using a strong reference to |service| to avoid circular reference. The lifetime
+    // of |service| must be longer than this LinkedCallback object.
+    static std::unique_ptr<LinkedCallback> Make(std::shared_ptr<Health> service,
+                                                std::shared_ptr<IHealthInfoCallback> callback);
+
+    // Automatically unlinkToDeath upon destruction. So, it is always safe to reinterpret_cast
+    // the cookie back to the LinkedCallback object.
+    ~LinkedCallback();
+
+    // The wrapped IHealthInfoCallback object.
+    const std::shared_ptr<IHealthInfoCallback>& callback() const { return callback_; }
+
+    // On callback died, unreigster it from the service.
+    void OnCallbackDied();
+
+  private:
+    LinkedCallback();
+    DISALLOW_COPY_AND_ASSIGN(LinkedCallback);
+
+    std::shared_ptr<Health> service();
+
+    std::weak_ptr<Health> service_;
+    std::shared_ptr<IHealthInfoCallback> callback_;
+};
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/android.hardware.health-service.example.rc b/health/aidl/default/android.hardware.health-service.example.rc
new file mode 100644
index 0000000..b393c58
--- /dev/null
+++ b/health/aidl/default/android.hardware.health-service.example.rc
@@ -0,0 +1,6 @@
+service vendor.health-default /vendor/bin/hw/android.hardware.health-service.example
+    class hal
+    user system
+    group system
+    capabilities WAKE_ALARM BLOCK_SUSPEND
+    file /dev/kmsg w
diff --git a/health/aidl/default/android.hardware.health-service.example.xml b/health/aidl/default/android.hardware.health-service.example.xml
new file mode 100644
index 0000000..98026cb
--- /dev/null
+++ b/health/aidl/default/android.hardware.health-service.example.xml
@@ -0,0 +1,7 @@
+<manifest version="1.0" type="device">
+    <hal format="aidl">
+        <name>android.hardware.health</name>
+        <version>1</version>
+        <fqname>IHealth/default</fqname>
+    </hal>
+</manifest>
diff --git a/health/aidl/default/health-convert.cpp b/health/aidl/default/health-convert.cpp
new file mode 100644
index 0000000..b5251f4
--- /dev/null
+++ b/health/aidl/default/health-convert.cpp
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "health-convert.h"
+
+namespace aidl::android::hardware::health {
+
+void convert(const HealthInfo& info, struct ::android::BatteryProperties* p) {
+    p->chargerAcOnline = info.chargerAcOnline;
+    p->chargerUsbOnline = info.chargerUsbOnline;
+    p->chargerWirelessOnline = info.chargerWirelessOnline;
+    p->maxChargingCurrent = info.maxChargingCurrentMicroamps;
+    p->maxChargingVoltage = info.maxChargingVoltageMicrovolts;
+    p->batteryStatus = static_cast<int>(info.batteryStatus);
+    p->batteryHealth = static_cast<int>(info.batteryHealth);
+    p->batteryPresent = info.batteryPresent;
+    p->batteryLevel = info.batteryLevel;
+    p->batteryVoltage = info.batteryVoltageMillivolts;
+    p->batteryTemperature = info.batteryTemperatureTenthsCelsius;
+    p->batteryCurrent = info.batteryCurrentMicroamps;
+    p->batteryCycleCount = info.batteryCycleCount;
+    p->batteryFullCharge = info.batteryFullChargeUah;
+    p->batteryChargeCounter = info.batteryChargeCounterUah;
+    p->batteryTechnology = ::android::String8(info.batteryTechnology.c_str());
+}
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/health-convert.h b/health/aidl/default/health-convert.h
new file mode 100644
index 0000000..179ffc4
--- /dev/null
+++ b/health/aidl/default/health-convert.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <aidl/android/hardware/health/HealthInfo.h>
+#include <batteryservice/BatteryService.h>
+#include <healthd/healthd.h>
+
+// Conversion between healthd types and AIDL health HAL types. Note that most
+// of the conversion loses information, because these types have a different
+// set of information.
+
+namespace aidl::android::hardware::health {
+
+void convert(const HealthInfo& info, struct ::android::BatteryProperties* out);
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/include/health-impl/HalHealthLoop.h b/health/aidl/default/include/health-impl/HalHealthLoop.h
new file mode 100644
index 0000000..c46aaa4
--- /dev/null
+++ b/health/aidl/default/include/health-impl/HalHealthLoop.h
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <memory>
+#include <optional>
+
+#include <aidl/android/hardware/health/IHealth.h>
+#include <health/HealthLoop.h>
+
+namespace aidl::android::hardware::health {
+
+class HalHealthLoop;
+
+class HalHealthLoopCallback {
+  public:
+    virtual ~HalHealthLoopCallback() = default;
+
+    // Called by HalHealthLoop::Init
+    virtual void OnInit(HalHealthLoop* hal_health_loop, struct healthd_config* config) = 0;
+    // Called by HalHealthLoop::Heartbeat
+    virtual void OnHeartbeat(){};
+    // Called by HalHealthLoop::PrepareToWait
+    virtual int OnPrepareToWait() { return -1; }
+    // Called by HalHealthLoop::ScheduleBatteryUpdate
+    virtual void OnHealthInfoChanged(const HealthInfo&) {}
+};
+
+// AIDL version of android::hardware::health::V2_1::implementation::HalHealthLoop.
+// An implementation of HealthLoop for using a given health HAL.
+class HalHealthLoop final : public ::android::hardware::health::HealthLoop {
+  public:
+    // Caller must ensure that the lifetime of service_ is not shorter than this object.
+    HalHealthLoop(std::shared_ptr<IHealth> service, std::shared_ptr<HalHealthLoopCallback> callback)
+        : service_(std::move(service)), callback_(std::move(callback)) {}
+
+    using HealthLoop::RegisterEvent;
+
+    bool charger_online() const { return charger_online_; }
+
+  protected:
+    virtual void Init(struct healthd_config* config) override;
+    virtual void Heartbeat() override;
+    virtual int PrepareToWait() override;
+    virtual void ScheduleBatteryUpdate() override;
+
+  private:
+    std::shared_ptr<IHealth> service_;
+    std::shared_ptr<HalHealthLoopCallback> callback_;
+    bool charger_online_ = false;
+
+    // Helpers of OnHealthInfoChanged.
+    void set_charger_online(const HealthInfo& health_info);
+
+    // HealthLoop periodically calls ScheduleBatteryUpdate, which calls
+    // OnHealthInfoChanged callback. A subclass of the callback can override
+    // HalHealthLoopCallback::OnHealthInfoChanged to
+    // broadcast the health_info to interested listeners.
+    // This adjust uevents / wakealarm periods.
+    void OnHealthInfoChanged(const HealthInfo& health_info);
+};
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/include/health-impl/Health.h b/health/aidl/default/include/health-impl/Health.h
new file mode 100644
index 0000000..e49f44c
--- /dev/null
+++ b/health/aidl/default/include/health-impl/Health.h
@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <memory>
+#include <optional>
+
+#include <aidl/android/hardware/health/BnHealth.h>
+#include <aidl/android/hardware/health/IHealthInfoCallback.h>
+#include <android/binder_auto_utils.h>
+#include <health-impl/HalHealthLoop.h>
+#include <healthd/BatteryMonitor.h>
+#include <healthd/healthd.h>
+
+namespace aidl::android::hardware::health {
+
+class LinkedCallback;
+
+// AIDL version of android::hardware::health::V2_1::implementation::Health and BinderHealth.
+// There's no need to separate the two in AIDL because AIDL does not support passthrough transport.
+//
+// Instead of inheriting from HalHealthLoop directly, implements the callback interface to
+// HalHealthLoop instead.
+//
+// Sample implementation of health HAL.
+class Health : public BnHealth, public HalHealthLoopCallback {
+  public:
+    // Initialize with |config|.
+    // A subclass may modify |config| before passing it to the parent constructor.
+    // See implementation of Health for code samples.
+    Health(std::string_view instance_name, std::unique_ptr<struct healthd_config>&& config);
+
+    ndk::ScopedAStatus registerCallback(
+            const std::shared_ptr<IHealthInfoCallback>& callback) override;
+    ndk::ScopedAStatus unregisterCallback(
+            const std::shared_ptr<IHealthInfoCallback>& callback) override;
+    ndk::ScopedAStatus update() override;
+
+    // A subclass should not override this. Override UpdateHealthInfo instead.
+    ndk::ScopedAStatus getHealthInfo(HealthInfo* out) override final;
+
+    // A subclass is recommended to override the path in healthd_config in the constructor.
+    // Only override these if there are no suitable kernel interfaces to read these values.
+    ndk::ScopedAStatus getChargeCounterUah(int32_t* out) override;
+    ndk::ScopedAStatus getCurrentNowMicroamps(int32_t* out) override;
+    ndk::ScopedAStatus getCurrentAverageMicroamps(int32_t* out) override;
+    ndk::ScopedAStatus getCapacity(int32_t* out) override;
+    ndk::ScopedAStatus getChargeStatus(BatteryStatus* out) override;
+
+    // A subclass may either override these or provide function pointers in
+    // in healthd_config in the constructor.
+    // Prefer overriding these for efficiency.
+    ndk::ScopedAStatus getEnergyCounterNwh(int64_t* out) override;
+
+    // A subclass may override these for a specific device.
+    // The default implementations return nothing in |out|.
+    ndk::ScopedAStatus getDiskStats(std::vector<DiskStats>* out) override;
+    ndk::ScopedAStatus getStorageInfo(std::vector<StorageInfo>* out) override;
+
+    // A subclass may override these to provide a different implementation.
+    binder_status_t dump(int fd, const char** args, uint32_t num_args) override;
+
+    // HalHealthLoopCallback implementation.
+    void OnInit(HalHealthLoop* hal_health_loop, struct healthd_config* config) override;
+    void OnHealthInfoChanged(const HealthInfo& health_info) override;
+
+    // A subclass may override this if it wants to handle binder events differently.
+    virtual void BinderEvent(uint32_t epevents);
+
+    // A subclass may override this to determine whether screen should be kept on in charger mode.
+    // Default is to invoke healthd_config->screen_on() on the BatteryProperties converted
+    // from getHealthInfo.
+    // Prefer overriding these to providing screen_on in healthd_config in the constructor
+    // for efficiency.
+    virtual std::optional<bool> ShouldKeepScreenOn();
+
+  protected:
+    // A subclass can override this to modify any health info object before
+    // returning to clients. This is similar to healthd_board_battery_update().
+    // By default, it does nothing.
+    // See implementation of Health for code samples.
+    virtual void UpdateHealthInfo(HealthInfo* health_info);
+
+  private:
+    friend LinkedCallback;  // for exposing death_recipient_
+
+    bool unregisterCallbackInternal(std::shared_ptr<IHealthInfoCallback> callback);
+
+    std::string instance_name_;
+    ::android::BatteryMonitor battery_monitor_;
+    std::unique_ptr<struct healthd_config> healthd_config_;
+
+    ndk::ScopedAIBinder_DeathRecipient death_recipient_;
+    int binder_fd_ = -1;
+    std::mutex callbacks_lock_;
+    std::vector<std::unique_ptr<LinkedCallback>> callbacks_;
+};
+
+}  // namespace aidl::android::hardware::health
diff --git a/health/aidl/default/main.cpp b/health/aidl/default/main.cpp
new file mode 100644
index 0000000..014ae34
--- /dev/null
+++ b/health/aidl/default/main.cpp
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/logging.h>
+#include <android/binder_interface_utils.h>
+#include <health-impl/Health.h>
+#include <health/utils.h>
+
+using aidl::android::hardware::health::HalHealthLoop;
+using aidl::android::hardware::health::Health;
+
+static constexpr const char* gInstanceName = "default";
+
+int main() {
+    // TODO(b/203246116): handle charger
+    // make a default health service
+    auto config = std::make_unique<healthd_config>();
+    ::android::hardware::health::InitHealthdConfig(config.get());
+    auto binder = ndk::SharedRefBase::make<Health>(gInstanceName, std::move(config));
+    auto hal_health_loop = std::make_shared<HalHealthLoop>(binder, binder);
+    return hal_health_loop->StartLoop();
+}