EyeGuard

EyeGuard is an Android eye-health guardian: on-device ML measures your face-to-screen distance, enforces the 20-20-20 rule— with Pro subscriptions powered by RevenueCat.

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Inspiration

I spend way too many hours on my phone — too close, too long, often in the dark. As a student I noticed my eyesight getting worse, and existing "eye care" apps were either just blue-light filters or manual timers that nobody sticks with. I wanted something that watches how you actually use your phone and intervenes at the right moment.

What it does

EyeGuard is an always-on eye-health guardian for Android:

  • Distance detection — every 30 seconds it briefly opens the front camera for a single frame, measures face-to-screen distance with on-device ML Kit face detection, and warns instantly if you're too close. The camera is released immediately; nothing ever leaves the device.
  • Ambient light monitoring — a low-power sensor listener warns when you're reading in the dark.
  • 20-20-20 rule — tracks continuous screen time via screen on/off events and reminds you to look 6 meters away for 20 seconds.
  • Smart eye comfort filter — a warm overlay that adapts to ambient light and night hours, toggleable from a Quick Settings tile.
  • Stats that motivate — daily screen time, too-close duration, longest continuous session, rest-compliance rate, weekly reports, streaks and achievements.
  • Built for real-world Android — battery-whitelist and auto-launch guidance for Chinese ROMs, battery-aware adaptive sampling, and boot-resume notifications.

How I built it

Native Android with Kotlin and Jetpack Compose (Material 3). CameraX + ML Kit for single-frame distance sampling, Room for daily usage stats, DataStore for settings, Hilt for DI, and a foreground service with a camera|specialUse type for the monitoring loop. Monetization is built with RevenueCat: the Pro plan unlocks custom thresholds, the smart filter, 7-day history charts, weekly reports and do-not-disturb hours.

Challenges I ran into

  • Chinese ROM background limits: foreground services get killed aggressively on MIUI/EMUI/Honor. I ended up combining a camera|specialUse FGS type with in-app guidance cards that deep-link users to battery whitelist and auto-launch settings.
  • Notification quirks: re-using a notification ID silently "updates" instead of alerting — reminders now always use fresh IDs, with a direct vibrator fallback for ROMs that swallow notification vibration.
  • Privacy-first camera usage: binding the camera for one frame per sample without a preview use case took some CameraX gymnastics, but it's what makes the feature battery- and privacy-friendly.

What I learned

Shipping a background-heavy health app is 20% features and 80% fighting the OS. I also learned how fast RevenueCat makes subscriptions: offerings, paywall logic and restore flows took less than a day to integrate.

What's next

Full-screen break overlays, sound alerts, and per-profile detection for shared devices.

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