Senior iOS/Android Location Tracking Engineer (Background Geofencing & Border Crossing Detection)

Senior Mobile Location Tracking Engineer Needed I’m the developer and owner of a mobile app called La Línea, which helps users track border crossing wait times between Mexico and the United States. The app is available on both iOS and Android and currently uses GPS-based crossing sessions to estimate border wait times. The Problem My biggest challenge is reliably detecting when a user has crossed the border and automatically ending their crossing session. Today, automatic detection works reasonably well when users grant “Always Allow” location permissions. However, many users choose: * iOS: “Allow While Using App” * Android: Foreground-only location access When this happens, the app may not always detect that the user has reached the finish zone near the border crossing. As a result: * Sessions may remain active too long * Wait times become less accurate * Users must manually reopen the app after crossing What I Need I’m looking for a highly experienced mobile location engineer to perform a deep technical review and help determine the best possible solution. Possible outcomes include: Option A Improve automatic session completion even when users only grant foreground/“while using” location permissions. Option B If fully automatic completion is not technically possible, trigger a push notification immediately when users enter the finish zone so they can reopen the app and complete the session. Option C Recommend a completely different architecture that improves reliability while respecting platform limitations. Existing System Current app architecture includes: * iOS app (SwiftUI) * Android app (Jetpack Compose / Kotlin) * Firebase backend * Firebase Cloud Functions * Firebase Cloud Messaging * GPS crossing sessions * Geofenced finish zones * Border crossing routes between Mexico and the United States The system already has: * Start zones * Finish zones * Session tracking * Location confidence scoring * Background location support for users who grant it What I’m Looking For Ideally you have experience with: * iOS Core Location * Significant Location Changes * Region Monitoring * Geofencing * Background execution limits * APNs * Android Fused Location Provider * Android Geofencing APIs * Background location restrictions * High-reliability location tracking systems * Transportation, logistics, navigation, fitness, rideshare, or similar location-based apps Deliverables 1. Technical audit of current architecture 2. Root-cause analysis of why sessions fail to auto-complete 3. Recommended architecture improvements 4. Optional implementation of the proposed solution When applying, please describe similar location-tracking projects you’ve worked on and your experience with iOS/Android geofencing and background location limitations.