I'm keeping my eye on this one too. We have an '07 Navi EL with Nav. I think I'm going to do a separate screen and mount it just above the rear view mirror.

Not sure if yours is wireless (from the front to back) but I'm inclined to run wires for better resolution and less interference. Seems like some of the screens have to be turned on every time you start the vehicle, but I want mine to come on automatically whenever reverse is engaged.

I'm intrigued by your trailer hitch mount idea but I wonder if it will give you the proper perspective on what's immediatly behind the vehicle?

Interesting idea to tap into the trailer harness.

Good luck!