OK, I have an '08 328 Coupe with I-Drive. I also have an iPhone 4s.
To get audio and control of the iPod part of the iPhone I needed a Y-adapter.
One end goes to the iPhone. The other end has a USB connector and a 1/8 inch stereo plug. Plug the iPhone in and both of the other connectors into the plugs in the center console. The USB plug is for control, the 1/8 inch stereo plug is for audio. BOTH must be plugged in to work.
Hope this helps.
It is my understanding that '09 and new will work with only the usb cable. Not positive on this though.
Craig (He's just this IT & Voice Over guy.)
The technical difficulty originally scheduled for this time has been postponed - due to technical difficulties.