Historical Audio Guide App

I need an experienced developer to create an audio guide app for historical places, available on both iOS and Android platforms. The audio should automatically trigger when the user is at a specific location.

Key Requirements:
- Location-based audio playback
- User authentication via email and password
- Backend feature for me to upload and manage the audio data

Ideal Skills:
- Mobile app development (iOS and Android)
- Experience with location services and geofencing
- Backend development for data management
- User authentication implementation

Please provide samples of similar work done.