See:

NAV-TV Corporation: VehicleDock

Also, on that page you can download the manual for more info.

If you also purchase an additional interface (like the BMW56CAN, which I picked up from TVNAv2GO here:

Mobile video mobile tv mobile video system mobile satellite tv mobile video systems nav tv car tv dvd car video car dvd car tv car video system car satellite tv video interface car navigation system car video navigation car navigation gps car tv scre

(tho you can also purchase it thru NAV-TV). This interface will allow for comtrol thru I-Drive and steering wheel buttons.