IMO I would not spend that amount of money when an after market GPS would cost a fraction of this price and would do the same job if not better. I personally installed a Garmin I5 on my X5 with no visible wire and the GPS automatically starts and stops with the ignition. This GPS does its job very well. In addition, since this unit works also on battery and includes a hard disk with all US and Canada, I can port it to another vehicle or to my bike in a matter of seconds. You can go for a more elaborate unit like the Garmin Nuvi 350 and still pay only a 4th of the BMW retrofit kit.
The following thread shows some pics of my installation. Look 4 or 5 posts down. http://www.xoutpost.com/x5-e53-forum/...elp-radio.html