Sync Reminder App

One Reminder App for all your devices. Sync Reminders provides seamless Android and iOS support with intelligent alerts that trigger at the right time and place.

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Sync Reminder

Inspiration

Most reminder apps are locked into one ecosystem or focus only on time-based alerts. In a multi-device world, switching between Android and iOS often breaks the experience.

We wanted to build a reminder app that works seamlessly across platforms — and reminds you not just when, but also where.

Smart reminders. Cross-platform. Reliable.

What it does

Sync Reminder is a cross-platform reminder app that supports both Android and iOS with real-time synchronization.

Key Features

  • ⏰ Time-based reminders
  • 📍 Location-based reminders (enter/exit triggers)
  • 🔄 Real-time device sync
  • 🔔 Reliable local notifications
  • 📱 Clean, minimal UI

System flow:

$$ Create \rightarrow Cloud\ Sync \rightarrow Device\ Listener \rightarrow Local\ Notification $$

Each device schedules notifications locally to ensure reliability even when offline.

How we built it

We built Sync Reminder using:

  • Flutter (single cross-platform codebase)
  • Firebase Authentication
  • Cloud Firestore (real-time listeners)
  • Flutter Local Notifications
  • Native Location Services

Reminder data structure:

$$ Reminder = { id,\ type,\ trigger,\ metadata,\ status } $$

Each device listens to Firestore updates and ensures:

$$ Local\ State = Cloud\ State $$

This keeps reminders consistent across devices.

Challenges we ran into

  • ⚙️ Different notification behavior on Android vs iOS
  • 🔐 Handling background location permissions (especially on iOS)
  • 🔄 Syncing cloud updates with locally scheduled notifications
  • 🌍 Managing time zone changes and device restarts

Ensuring consistency required careful state reconciliation.

Accomplishments that we're proud of

  • ✅ One Flutter codebase for Android & iOS
  • ✅ Real-time cross-device synchronization
  • ✅ Accurate time and location triggers
  • ✅ Clean, intuitive UX
  • ✅ Production-ready architecture

What we learned

  • Cross-platform does not mean identical platform behavior
  • Background execution requires deep system understanding
  • Real-time systems need clear state ownership
  • Reliability is more important than feature count

What's next for Sync Reminder App

  • 🏃 Health goal-based reminders (steps, calories, target verification)
  • 📍 Advanced background geofencing optimization
  • ⚡ Performance improvements for large reminder sets
  • 👥 Shared reminders for families & households
  • 🧠 Smart categories & AI scheduling suggestions
  • 💳 Family subscription plans

Our goal is to evolve Sync Reminder into a lightweight productivity companion that works everywhere.

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