With v1.5, I had music streaming through my mono bluetooth headset. By dialing one of the special dialing characters "w" or "p" ("***" or "**"), my Eris opened a connection with my headset without placing the call. I was then able to play music, either streaming over the web or an mp3 player, until a call came in. The phone would override the music until the call was completed - just like it does when playing music over the speaker. It was sometimes a little quirky to get it to reestablish the bluetooth connection, but while it worked, it was wonderful.
Now, 2.1 is too smart to establish the bluetooth connection until after the call is established. I'm bumming! I can't find a way to go back to 1.5 either.
HTC tech support said that it's a software setting that restricts playing music through anything not stereo. If we could locate it, I would think we could create a work-around fairly easily. As I've never programmed unix or hacked my Eris (yet), anyone know how to proceed? People are ready and willing to pay for this fix!!