External bluetooth audio into Media app

I would like to see an extension to the Media app allowing bluetooth units (like tablets or phones) to connect and play audio. Text info showing attached unit and media tags would be nice (but not necessary).

Why?

My older phone is now my car infotainment system and it handles the duty well. …except for allowing bluetooth units to connect. The connection to the car amplifier and speakers is done with a cable so bluetooth is free to be used for audio input.