Device Watch

Device Watch is an Android device monitoring app with a Jetpack Glance home screen widget, per-app usage insights (screen time, data, notifications and more), and an interactive screensaver for charging or docked use.

The default app language is English. Finnish users get a localized app name and UI through Android's values-fi resources.

Features

• Home screen widget for battery, memory, CPU, storage, Wi-Fi, mobile network, data usage, uptime, today's screen time, and last update time
• Tapping the widget anywhere opens the app
• Data counters per calendar day or per one-month billing cycle with a configurable start day (month lengths handled automatically); the selection applies to the widget and the in-app data rows
• Tabbed dashboard UI: Overview (live battery ring, usage counters, RAM/CPU/storage meters and data counters — full widget parity for people who skip the widget), Apps (usage insights), Device (hardware, SIM and Wi-Fi details), and Settings
• Apps tab: Digital-Wellbeing-style screen-time donut (top apps + others) with tappable legend, top data consumers today, and a last-opened list (oldest and never-used apps first, reversible) with per-app uninstall; home-screen launchers excluded from usage rankings
• Per-app detail sheet: screen time, times opened, last opened, data used and notifications today
• Usage counters on the Overview tab, scoped to the same day/billing-cycle setting as the data counters: total screen time, screen unlocks (API 28+), a filtered notification count (ongoing notifications, group summaries and updates to an existing notification are not counted, so the number stays believable), device restarts and charging sessions
• The app keeps its own 62-day daily history for these counters (Android has no retroactive API): unlocks and screen time are backfilled from the ~7 days Android remembers, restarts are derived from BOOT_COUNT deltas (immune to Android re-delivering BOOT_COMPLETED after app updates), and notification/charging tallies accumulate from install onward
• On-device notification log with app name, timestamp, title, and text; 7-day retention; tapping an entry opens the app that posted it (when still installed)
• History page (opened from the usage card) listing exact daily values for the retained 62 days — screen time, unlocks, notifications, device restarts, and charging sessions; each metric states since when it has been collected, and the page refreshes itself while open
• Since-charge page (opened from the battery card): the period since the battery was last charged full — or since the charger was unplugged, when charging stopped short of full — with elapsed time, battery drop and average drain, unlocks, notifications, Wi-Fi/mobile data, and a per-app screen-time donut over that window (Android does not expose real per-app battery percentages to third-party apps, so the page shows honest usage numbers instead)
• Today's screen time also appears in the widget footer, refreshed at most once a minute so the 5-second widget loop stays untouched
• Most-opened-today list on the Apps tab, and last-opened rows show the clock time for apps used today (following the system 12/24-hour setting) with two-tier staleness colors: amber after 1 month unused, red after 3 months (Google's app-hibernation threshold) or never used
• Special-access buttons show a green/red status dot for granted/missing access
• Privacy dashboard shortcut for per-app location/microphone/camera usage (system view; that data is not exposed to third-party apps)
• Interactive Android screensaver with a large clock, date, next alarm, charging status, battery percentage, voltage, temperature, and live charging power in watts
• Screensaver clock follows the device 12/24-hour setting, with a second-aligned tick
• Battery-level-tinted background gradient and a softly pulsing charge indicator in the screensaver
• Optional screensaver dimming: manual, or automatic on a configurable night schedule (default 22:00–07:00)
• Remembered screensaver rotation setting for repeated charging sessions; the background gradient mirrors with the 180° layout swap
• Larger screensaver rotation touch target for easier use
• Battery full notification while the screensaver is active
• English default resources with Finnish localization
• Runtime permission handling for location, phone state, nearby Wi-Fi devices, and notifications
• Usage Access shortcut for network and app-usage statistics
• Release build configured with R8 minification and resource shrinking

Every metric is real data read from Android and kernel sources. When a value is not available with the permissions granted, the UI shows a dash (—) instead of a fabricated value.

Download

Download the latest signed APK from the Releases page and open it on your device to install. Because every release is signed with the same key, later versions install cleanly as an update over an existing one.

Requires Android 8.0 (API 26) or newer.

Architecture

The app follows an MVVM + repository structure with Hilt dependency injection.

presentation/   DashboardViewModel + AppsViewModel (StateFlow UI state)
presentation/ui Compose-only screen code: SystemDashboardScreen scaffold with a
                Material 3 NavigationBar, Overview/Apps/Device/Settings tabs and
                shared components (SettingsSectionCard, DeviceInfoRow, AppIcon,
                ScreenTimeDonut, AppDetailSheet)
data/           SystemStatsRepository + AppUsageRepository (per-app usage, on demand)
                AppSettingsRepository (data-counter mode, cycle start day, sort order)
                NotificationStats + UsageHistory (own daily tallies, 62-day retention)
                SystemStatsParser, DataPeriodCalculator, UsageEventAggregator,
                NotificationCounting (pure, unit-tested calculations)
                SystemStats / AppUsage models (+ UNAVAILABLE_* sentinels)
widget/         Glance DashboardWidget, WidgetStateUpdater (DataStore writes),
                WidgetController (port the ViewModel talks to), receiver and actions
system/         SystemMonitorService (foreground), MonitorDreamService (screensaver),
                NotificationCounterService (notification listener)
di/             Hilt modules and entry points

• SystemStatsRepositoryImpl is the single source of truth. It is a @Singleton, reads system/kernel sources off the main thread on an injected dispatcher, and serializes its CPU-load snapshots with a Mutex.
• SystemDashboardScreen observes the ViewModels with collectAsStateWithLifecycle() and obtains them via hiltViewModel(). The four tabs are flat destinations switched with saveable tab state (no navigation library); each tab keeps its own scroll position. Permission requests and the foreground-service start stay at screen level.
• Services and the widget receiver use @AndroidEntryPoint; the Glance ActionCallback reaches the graph through a Hilt EntryPoint.

Tech Stack

• Kotlin 2.4, AGP 9.2.1, Gradle 9.6
• compileSdk 36, minSdk 26, targetSdk 35
• Jetpack Compose (BOM 2026.06.00) + Material 3, Jetpack Glance 1.1.1
• Hilt 2.60 with KSP 2.3.9
• AndroidX Lifecycle 2.10, Activity 1.13, DataStore 1.2, WorkManager 2.11
• Dependencies are managed through the gradle/libs.versions.toml version catalog

Language Behavior

Android selects the UI language from resource qualifiers:

• English and every non-Finnish device language use app/src/main/res/values/strings.xml
• Finnish devices use app/src/main/res/values-fi/strings.xml

Permissions

The app requests only permissions that are used by the current feature set:

• RECEIVE_BOOT_COMPLETED
• FOREGROUND_SERVICE
• FOREGROUND_SERVICE_SPECIAL_USE
• POST_NOTIFICATIONS
• ACCESS_NETWORK_STATE
• ACCESS_WIFI_STATE
• ACCESS_COARSE_LOCATION
• ACCESS_FINE_LOCATION
• NEARBY_WIFI_DEVICES
• READ_PHONE_STATE
• PACKAGE_USAGE_STATS
• QUERY_ALL_PACKAGES (resolve names/icons for the per-app data list; the app is distributed outside Google Play)
• REQUEST_DELETE_PACKAGES (uninstall from the last-opened list via the system dialog)

Notification counting additionally uses the optional Notification access special permission (a NotificationListenerService); counting starts when access is granted. Do Not Disturb and Bluetooth control permissions are not requested.

Building

Use the Gradle wrapper from the repository root:

.\gradlew.bat :app:compileDebugKotlin
.\gradlew.bat :app:testDebugUnitTest
.\gradlew.bat :app:lintDebug
.\gradlew.bat :app:assembleDebug
.\gradlew.bat :app:assembleRelease

Release builds are minified with R8 and resource shrinking. The release APK is unsigned unless a local keystore.properties and keystore are present.

Testing

JVM unit tests cover the pure parsing/maths and the ViewModel:

.\gradlew.bat :app:testDebugUnitTest

• SystemStatsParserTest — CPU-load deltas, frequency residency/pressure, battery wear, mobile-generation mapping, Wi-Fi SSID/band, signal filtering
• DataPeriodCalculatorTest — billing-cycle period math (start-day clamping across month lengths, leap February, year rollover)
• UsageEventAggregatorTest — foreground-session folding (in-app activity switches, unclosed sessions), donut segments, last-use sorting, day math, staleness tiers and launch-count ranking
• NotificationCountingTest — the "real notification" filter and count retention/purging
• UsageHistoryLogicTest — BOOT_COUNT delta dedup and history-key retention
• WidgetFormattingTest — widget display formatters (locale-pinned), adaptive MB/GB data amounts
• DashboardViewModelTest — refresh, opacity load/commit, data-counter settings, daily counters, widget-installed flag (hand-written fakes)
• AppsViewModelTest — Apps-tab loading, empty state without usage access, detail assembly, sort toggle persistence
• ClockFitTest — screensaver clock width-fit math
• DreamLogicTest — night-dim window (incl. crossing midnight) and charging-wattage normalization

Build Outputs

app/build/outputs/apk/debug/app-debug.apk
app/build/outputs/apk/release/app-release.apk

APK and signing files are intentionally ignored by Git.

Project Structure

app/src/main/java/com/example/modernwidget/
  MainActivity.kt
  MonitorApp.kt
  data/
    AppSettingsRepository.kt
    AppSettingsRepositoryImpl.kt
    AppUsage.kt
    AppUsageRepository.kt
    AppUsageRepositoryImpl.kt
    BatteryStatusReader.kt
    ChargeAnchor.kt
    ChargeAnchorStoreImpl.kt
    DataPeriod.kt
    NotificationCounting.kt
    NotificationLog.kt
    NotificationLogImpl.kt
    NotificationStats.kt
    NotificationStatsImpl.kt
    SystemStats.kt
    SystemStatsParser.kt
    SystemStatsRepository.kt
    SystemStatsRepositoryImpl.kt
    UsageEventAggregator.kt
    UsageHistory.kt
    UsageHistoryImpl.kt
  di/
    DispatchersModule.kt
    RepositoryModule.kt
    RepositoryEntryPoint.kt
  presentation/
    AppsViewModel.kt
    DashboardViewModel.kt
    HistoryViewModel.kt
    SinceChargeViewModel.kt
    ui/
      AppDetailSheet.kt
      AppsTab.kt
      DashboardComponents.kt
      DashboardTabs.kt
      DeviceTab.kt
      HistoryListLogic.kt
      HistoryPage.kt
      OverviewTab.kt
      ScreenTimeDonut.kt
      SettingsTab.kt
      SinceChargePage.kt
  system/
    BatteryFullNotifier.kt
    DreamPreferences.kt
    MonitorDreamService.kt
    NotificationCounterService.kt
    SystemMonitorService.kt
  widget/
    DashboardWidget.kt
    DashboardWidgetReceiver.kt
    RefreshStatsAction.kt
    WidgetController.kt
    WidgetStateUpdater.kt

app/src/test/java/com/example/modernwidget/
  data/ChargeAnchorLogicTest.kt
  data/DataPeriodCalculatorTest.kt
  data/NotificationCountingTest.kt
  data/NotificationLogCodecTest.kt
  data/NotificationLogImplTest.kt
  data/SystemStatsParserTest.kt
  data/UsageEventAggregatorTest.kt
  data/UsageHistoryLogicTest.kt
  presentation/AppsViewModelTest.kt
  presentation/DashboardViewModelTest.kt
  presentation/Fakes.kt
  presentation/HistoryViewModelTest.kt
  presentation/SinceChargeViewModelTest.kt
  presentation/ui/HistoryListLogicTest.kt
  system/ClockFitTest.kt
  system/DreamLogicTest.kt
  widget/WidgetFormattingTest.kt