As a subscriber to this site you can download all the TSBs and other documents which include a complete wiring diagram package. I checked the other day and found the NAV wiring diagram. It shows two wires: one for the speed sensor which I assume disables the NAV functions, and one for the reverse indicator which switches on the camera. I haven't finished tracing those wires yet but once I confirm them I plan to go inside the dash and snip the wires then route them to some mini toggle switches on the dash panel so I can enable or disable either feature set on demand. Once I can activate the camera circuit on command I plan to add a video switching device that will allow me to play normal DVDs, feed in two external wireless cameras that I mount on the bed rails, or activate the backup camera at any time. I also have to handle the sound somehow but I will figure it all out before I cut the first wire. Will be sweet to get it done.