Custom GPS Tracker App

I own the GPS tracker shown here: https://www.alibaba.com/product-detail/subject_62553862078.html?from=share&ckvia=share_2af4031047d24c938f874c81c173f3f1 and have full access to its open-source firmware and communication protocol. I now need a polished mobile application, built once and shipped natively to both iOS and Android, that talks directly to this device and brings the data to life for end-users. Core functionality must include: • Real-time location updates on a smooth map view. • Configurable geofences that trigger push notifications the moment the tracker crosses a boundary. • A clean, scrollable history screen where users can replay routes for any chosen date and time range. Users will sign in with a simple username-and-password flow, so the app should ship with a lightweight authentication backend (Firebase Auth, Supabase, or a similar plug-and-play service is fine). All device commands and data packets are already documented in the manufacturer’s GitHub repo; I will share that repo and sample API calls once we start. I’m open to native Swift/Kotlin or a high-quality cross-platform stack such as Flutter or React Native—whichever lets you deliver a responsive UI, battery-friendly background location handling, and rock-solid push notifications. Deliverables: • Source code (iOS + Android) ready for App Store and Google Play submission. • Brief setup guide so I can compile and rebrand in the future. • Post-launch bug-fix window to iron out any edge cases that appear in the field. If you’ve previously integrated hardware trackers or built mapping apps, that will help us move quickly. Let me know your preferred stack, estimated timeline, and any clarifying questions you have once you’ve reviewed the device docs.