Wanted to know if this was possible or if anyone has had it done? It seems like it would be easy to link one to the nav unit.

If you can find a shop with some know how and ingenuity they may be able to help you.
Here is a schematic of the back of the Navigation with what wire does what.

Maybe wires (12, 13 & 14) on Connector C

(IMG:http://img178.imageshack.us/img178/4160/snfbe8116n.gif)

I'm temped to try this...

I've done some poking around and like i360 suggested, wires 13/14 on connector c. Since most backup cams use an rca wire, it would make the most sense... RCAs have a positive and ground. I would put the positive in 14 and ground in 13. Although that #12 wire does throw me off... wth does that do? lol... anyways, I saw on a korean site that the wires they tapped into were the video in and the usb +/- but I would think that's more for a rear view camera that is always on instead of a reverse camera that would only turn on when you're in reverse...