One comment about the belkin unit that I experienced.
The sound wasn't as nice as I thought so I returned and instead got a JVL Bluetooth unit sold at best buy or amazon (cheaper) JVC KS-BTA100 wich is made for the jvl head unit but works just fine in my 08 335i using the aux port. I also had to hard wire to the cigarrete lighter conector as it doesnt come with the adaptor. The sound with this unit is a lot better from my experience but still not the same as if you where to just plug in your ipod, iphone, mp3. other plus is the controls works perfect with my iphone 4s it fast forward skips songs and pause, It also has the ability to make and receive call but i don't use it as i have bluetooth with the car.