I have the Aux setup in my X5. I had a cable connector that connected to the docking part of my ipod. Works great. I got an iphone and tried to connect the iphone to the aux location using my cable. It would not play through the stereo and only played through the iphone. Hmmmmmm???
Went to the Man, Tom G at EAS, and asked why it would not play.
Per Tom: iPhones use a 3-ring 3.5mm jack instead of a standard 2 ring.
I sourced a cable from cablesonline for $7.99 (Audio and Sync Cable for iPhone / iPod(Apple Dock Connector to USB / 3.5mm Audio)).
Works perfectly. Hope this info helps any iphone/aux users out there.
Most important thank you to Tom G. He has helped me out over the years and is a great resource for this forum. I am simply reporting the info that he provided to me. Thanks Tom!

Tom's info below:
Tom G. | european auto source (eas)
email:
[email protected] web:
european auto source - 714.369.8524 | how fast can we make your dream go, stop and corner?
tel 866.669.0705 | ca: 714.369.8524 x22 | fax: 714.908.1796