I'm a first time poster but have been reading these forums all day now. Like many of you I'm sure you hate the fact that you can't control your music with your iPhone when you connect it to your BMW stereo.
I found a simple solution for this and now I can control my iPhone music through my car stereo controls & my iPhone menu.
All you have to do is JailBreak your iPhone (if you don't know how just ask and I'll explain) and install an Application through the Cydia store called "NoAccessorySplash".
Once installed you now have gained full control of your iPhone again while controlling your stereo!