Matt, I thought I'd run another product by you again, but let me get something straight before I do.

On your phone/OS, can you specify which external BT device will be used for AVRCP and A2DP even when you have two devices that support both, or one device that supports both and the other only A2DP?

I have a small A2DP/AVRCP device that was pretty cheap ($13) that you might be able to use as a remote if you can set it up for only its remote use. It's about the size of an iPod shuffle and has the same type of buttons on it. Play/Pause and then 4 directions for track changing and volume.

http://www.dealextreme.com/p/bluetooth-2-0-a2dp-avrcp-stereo-music-receiver-and-handsfree-black-8422

If you're actively listening to music through it, the battery only lasts for around 2 hours. I don't have any clue how long it would go just using it as a remote.