With the help of tompak23d's post in another thread, I found another option:
http://www.kufatec.de/shop/product_i...ro----BMW.html
This would do exactly the same thing as the original Bluetooth-HF -option AND also support A2DP. I wish I had a way of testing whether the A2DP is at all adequate for listening to music, and how horrible it would be UI-wise, trying to control the playback from the phone.
I really prefer the OEM-look, but without iDrive, the UI sucks bad. Wish BMW would include iDrive also without NAV, like Audi does with their MMI...