I have an iPhone 3G and it is paired with 5 different BT devices (not at the same time of course). For this discussion, one device is a BT handsfree by Plantronics, the other is my 2010 Mazda 3 that supports handsfree and headset (streaming music) profiles. Both Plantronics and Mazda work fine, but here is my issue:
I am on a call using my Plantronics hands free headset, I walk out of the house, get into the car and start it. The iPhone pairs with Mazda and disconnects the plantronics so that now my call is coming through the car audio. I was not able to switch back to the headset - it was not available in the "source" menu during the call, and going to BT settings it would not reconnect even when I deleted the mazda. Until I ended the call, I could not connect to the Plantronics.
Anyone else see this behavior? I know some would like it, but I had others in the car and they wanted the radio, not my conference call. I don't have much hope that I can change this behavior, but I thought it strange that the phone picked a new source without asking me.