I know pretty much nothing about the BT protocol (just familiar with the high-level concept) so tell me if this would work.

Your BT enabled phone rings and sends a signal to your wireless headset telling it to turn on. The empeg's BT module also hears this (promisc?) and auto-mutes the player. When the conversation ends, the empeg starts playing again.

Maybe with a bit of coding, write something for a phone with both BT and Java. When the phone rings, the caller ID info is sent to the empeg. The music fades down, and the caller's name is either TTS'd or you have a WAV file for your frequent callers and one of those is played. That ends, the music is paused and 2 rings have gone by.... your phone's auto-answer now kicks in. You hear a short beep through your wireless headset (which you were already wearing because you were expecting a call) queing you to say "Hey, Chris!" without having taken your hands off the wheel or your eyes off the road!