Audio and sound mixing

Summary: The goal is to develop a light-weight mobile app to allow recording ambient sound via the built-in microphone on various types of headphones while at the same time being able to listen to music. When Bluetooth headphones are used, the connection (on Android phones) is generally established via an SCO link that limits the input sample-rate to 8 kHz. We are looking for a way (using Bluetooth 5.2 or RFCOMM sockets) to go beyond these artificial limitations without the necessity for the end user to root their phone (e.g. for the implementation of a custom Bluetooth stack). 

Platform: Android and/or iOS 

Required features: 
- Simple, intuitive UI with minimal options 
- Remains active in background when device is locked, or another app is opened 
- Allows mixing of audio streams with background apps so that music can be streamed through other apps while recording audio with this app 
- Hardware agnostic, i. e. can connect through any/most headphones via standard protocols such as Bluetooth 
- Stream collected data to remote location on in-house server or cloud storage 
- When connected via Bluetooth, allow CD quality input stream (44.1 kHz sample rate) on both iOS and Android Bluetooth stacks  
- Should run on Android 11 and above (if possible)