• 

  Maps tab

• 

  Network tab

• 

  Alerts tab

Sift — Hackathon Submission

Inspiration

Disasters often take down connectivity first. We wanted one app that fetches real disaster data when online and shares it device-to-device over Bluetooth when the network is out.

What it does

Sift aggregates live disaster alerts from USGS, NOAA, NASA EONET, and GDACS. A server-side AI agent deduplicates and stores them; connected phones get alerts in real time over WebSocket. When there’s no internet, phones form a BLE mesh: they advertise and scan for other Sift devices and relay alerts and chat locally. Alerts are shown in a list and on a map.

How we built it

Backend: FastAPI + Uvicorn, scheduled AI agent hitting the above APIs plus Tavily, WebSockets for push, JSON storage. Client: React Native (Android/iOS) with react-native-ble-plx and react-native-multi-ble-peripheral for central + peripheral BLE. One WebSocket per device on client and server to avoid duplicate connections.

Challenges we ran into

The client was opening multiple WebSockets (re-renders/Strict Mode), causing duplicate registrations and status flicker—we fixed it by closing the previous socket before opening a new one and only treating the “current” socket’s close as a disconnect. We also hit 404 on /ws because the client was hitting port 80 (nginx) instead of the FastAPI port; we fixed the URL and documented firewall rules. On the server we used a venv to work around externally-managed Python and added logic to close old connections when the same device reconnects.

Accomplishments that we're proud of

End-to-end flow from multiple APIs and AI to real-time push and BLE relay. Offline-capable alerts and chat. One React Native codebase for both platforms with a clear split between server (aggregation, push) and client (UI, local storage, mesh).

What we learned

WebSocket lifecycle needs one active socket per client and careful handling of “current” vs replaced sockets. BLE central + peripheral in one app works with the right RN libraries. Firewall and port config are easy to miss when moving off localhost.

What's next for Sift

Multi-hop BLE relay, backend, location-based alert filtering, simple history/trends, and native push when the app is in the background.

Built With

• amd
• android-studio
• fastapi
• ios
• react-native
• xcode