Parrot have announced their MK6000 Car Kit which incorporates A2DP Bluetooth Audio streaming. 

I was looking for a BT Car Kit when I bought my new car but ended up getting an integrated phone module instead - this unit is seriously tempting !

I'd love to be able to stream the audio from my Windows Mobile device to the car!

You can see more details at:

http://www.parrot.biz/usa/products/parrotmk6000