I did a test setup and it worked perfectly. I found the wire that supplies voltage to the reverse light when the car is in reverse by testing each wire with a test light. I then used my home-made test wires ( just a simple wire with 2 alligator clamps on each end ) with long wire going to the "reverse" wire on the radio. When put in reverse, the radio screen automatically changes to display the reverse camera screen and when put in gear or neutral it goes back to whatever was last on screen (tv/iPod/USB/GPS/DVD/radio).
I will wire it up properly with the wire going under the rear seat and carpet. I'm also going to re-wire my steering wheel controls since I have the radio out.
Thanks for your help guys.