I’m building a mobile application that lets people broadcast text-only messages to everyone inside a geographic zone they draw on the map. The moment a user enters, exits, or simply stands within that zone, the message should arrive instantly; anyone outside the boundary stays silent. Zones are created on-the-fly by the user—think free-form circles, polygons, or any latitude/longitude shape they need—so the system has to watch position changes continuously without draining the battery. The app must run natively on both iOS and Android and feel identical on each platform. I’m comfortable if you work in React Native, Flutter, or separate native stacks, as long as the final builds pass App Store and Google Play review. Behind the scenes a lightweight backend should store active zones, push new messages through APNs/FCM in under two seconds, and expire or archive old broadcasts automatically. Deliverables • Universal iOS + Android app with map interface for drawing, editing, and deleting custom zones • Realtime text message delivery engine (WebSockets or pub/sub) integrated with push notifications • Scalable backend/API with basic admin dashboard to view zones and traffic • Source code, build instructions, and a short test plan covering edge-cases like overlapping zones and rapid movement Acceptance criteria 1. A device inside a zone receives the text within 2 s, verified over 4G and Wi-Fi. 2. Moving outside the boundary suppresses further pushes until re-entry. 3. Battery usage for continuous location tracking stays under 5 % per hour in a field test. 4. App passes TestFlight/Internal Testing with no blocking crashes. If you’ve worked with Google Maps SDK, MapKit, Firebase Cloud Messaging, or similar tooling, this should feel familiar. Let’s create a smooth, real-time, location-aware messaging experience.