Remindr

Inspiration

Switching phones shouldn't mean losing your reminder system. Today’s reminder apps are either platform-locked, lack advanced recurrence, fail to clear notifications across devices in real-time, or break under poor network conditions. Professionals, students, and families need a reminder system that works reliably across devices — online or offline.

What it does

Remindr is a cross-platform reminders app designed for users who need more than basic functionality:

Core Reminder Features:

• Smart Snooze: Custom snooze intervals directly from notifications (e.g., "in 22 minutes"), eliminating arbitrary time constraints.
• Advanced Recurrence: Support for complex patterns including "Every 3 days," "Second Tuesday of the month," and "Weekdays only."

Sync & Reliability:

• Real-Time Cross-Platform Sync: Complete a reminder on one device and see it update instantly across all platforms—even clearing the notification from other devices' screens.
• Offline-First Architecture: Full functionality without internet connectivity, with automatic sync when connection is restored.

Organization & Discovery:

• Tags & Categories: Flexible organization system allowing users to categorize and filter reminders across multiple dimensions.
• Multiple Views: Switch between daily, weekly, monthly, and agenda views to visualize reminders in the format that matches your workflow.
• Insights Dashboard: Analytics showing completion patterns, productivity trends, and reminder distribution to help users understand and optimize their habits.
• Subtasks & Attachments: Break down complex reminders into actionable steps and attach relevant files, photos, or documents directly to reminders.

How we built it

We chose Flutter for true cross-platform development with a single, maintainable codebase:

• Frontend: Flutter with Riverpod for predictable state management and GoRouter for declarative navigation
• Backend: Supabase provides authentication, real-time database capabilities, and secure storage
• Local Database: Drift (SQLite) ensures offline functionality and local data persistence
• Monetization: RevenueCat manages cross-platform subscription infrastructure and entitlement logic
• Sync Engine: Custom-built synchronization system with conflict resolution and offline queue management

Challenges we ran into

Building a robust sync engine proved to be our most significant technical challenge. Implementing offline-first architecture with real-time synchronization and intelligent conflict resolution required designing a queue system that tracks all changes with timestamps and resolves conflicts using last-write-wins logic. This foundation was essential for delivering our "complete once, updates everywhere" promise.

Cross-platform notification reliability presented platform-specific complexities. Android's diverse ecosystem—with variations in WorkManager, AlarmManager, and manufacturer-specific battery optimization—required extensive testing and platform-specific implementations to ensure notifications fire consistently and on time.

Subscription management across both app stores demanded careful configuration and thorough testing of purchase, restore, and entitlement flows to ensure a seamless cross-platform experience.

Accomplishments that we're proud of

• Delivered true real-time sync where completing a reminder on one device updates all others instantly, including automatically clearing notifications on other active devices.
• Implemented custom snooze actions accessible directly from system notifications on both iOS and Android
• Built support for complex recurrence patterns while maintaining offline-first performance and reliability

What we learned

• Local-first architecture is foundational for building user trust and ensuring reliability across diverse network conditions
• Synchronization complexity scales exponentially with offline support and conflict resolution requirements
• Platform-specific notification behavior varies significantly across Android OEMs and requires targeted optimization
• Cross-platform subscription flows need comprehensive testing across both app store environments to ensure reliability

What's next for Remindr

• Collaboration Features: Shared reminder lists for families and teams with granular permissions
• Web Application: Full-featured web client for desktop workflows
• Intelligent Scheduling: ML-powered suggestions for optimal reminder timing based on user patterns
• Enhanced Privacy Controls: Per-list visibility settings and optional local-only mode for sensitive reminders

Built With

• dart
• drift
• fcm
• firebase
• flutter
• gotrue
• postgresql
• realtime
• revenuecat
• sql
• supabase