Loop - Reminders & Nagging

Persistent reminders that nag you until it's done. Cross-device sync, custom notification snoozes, and powerful recurrence — so you never miss what matters.

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Inspiration

I kept missing reminders. Not because I forgot to set them — but because they were too easy to dismiss. One swipe and gone. If you use multiple devices, it gets worse: dismiss on your phone, still buzzing on your tablet.

I wanted a reminder app that actually refuses to let me forget. Something that nags persistently until I act on it. And I wanted it to work across all my devices — iOS and Android — with real-time sync.

The RevenueCat Shipyard hackathon was the perfect push to build it.

What it does

Loop is a cross-platform reminders app with three core features:

  • Persistent Nagging — Reminders re-alert at configurable intervals (default: every 5 min) until you explicitly mark them done or snooze. No more "swipe and forget."
  • True Cross-Device Sync — Create on your phone, see it on your tablet in seconds. Complete it anywhere, cleared everywhere. Works offline too.
  • Powerful Recurrence — Daily, weekly (specific days), monthly, yearly, or hourly intervals. Far beyond "repeat daily."

Plus sub-3-second task entry, custom notification snooze actions (5 min / 15 min / 1 hour) directly from the notification shade, and organized lists.

How I built it

  • Flutter + Dart for cross-platform (iOS & Android from one codebase)
  • Drift (SQLite) as the local database for offline-first, zero-latency UI
  • Cloud Firestore for real-time cross-device sync with conflict resolution
  • Firebase Auth (Google, Apple, Anonymous sign-in)
  • RevenueCat for subscription management — freemium model with monthly/yearly plans and a 7-day free trial
  • Clean Architecture with flutter_bloc for state management

The offline-first approach was key: every action writes to the local DB immediately, then queues for Firestore sync. The UI never waits for the network.

Challenges I faced

  • iOS 64-notification limit — Had to build a smart scheduling system that prioritizes the soonest reminders and reschedules on app resume
  • Background notification actions — Making "Done" and "Snooze" buttons work when the app is terminated required careful Dart isolate handling
  • Offline sync conflicts — Implementing last-write-wins with proper reconciliation, especially protecting default lists from accidental deletion
  • Anonymous-to-authenticated migration — Preserving all local data when a user signs in for the first time

What I learned

Building an offline-first sync system is significantly harder than a simple cloud-backed app. The edge cases around conflict resolution, queue processing, and cross-account data isolation taught me a lot about distributed systems at the mobile level.

What's next

  • Home screen widgets (iOS + Android)
  • Siri / Google Assistant integration
  • Location-based reminders
  • Shared lists for family and teams
  • Apple Watch / Wear OS companion apps

Built With

  • apple
  • cloud-firestore
  • dart
  • drift
  • firebase-auth
  • flutter
  • flutter-bloc
  • google-sign-in
  • material-3
  • revenuecat
  • sign-in
  • sqlite
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