I think you'll find it quite difficult to get your car to receive A2DP (audio) from one device but also be paired with another device so it can send AVRCP commands (play/pause/next etC).

Maybe try looking for a CAN BUS monitor that can pick up button presses. There's no USB host on the empeg though right (it's been so long)?

Either way is a long road I think you'll find.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)