iPod/MP3 device adapter
I spent about $500 (parts & labor) to have my custom audio installer do it here in the Chicago suburbs. He's done a lot of work on my E63 (2005), including installing the Escort 9500ci integrated radar/laser system. Very clean work.
If you need, I can get the make/model of the unit. I think there are only 1 or 2 options for this on the market given the complexity of the fiber connectors of the BMW radio unit.