I just did this install yesterday using a Garmin BC20 wireless camera linked to my dezl760 GPS. I installed the camera to the inside window frame using a home made attachment plate (small piece of aluminum). I then powered the wireless transmitter via a 12vdc plug that is already installed in the back of the RV. The link to the GPS is solid and I am really happy with this arrangement. A big advantage that I have by getting power from a 12v plug is that the unit is now portable. I can move it from vehicle to vehicle in minutes. Also, by having 12v power, I can have the camera on at all times so that I can view traffic behind me while under way. This helps with lane changing. If I had wired it to power from the back-up lights, then it would have only worked when the vehicle was placed in reverse.
I cannot attest to other wireless camera systems, but the garmin set up works extremely well for me. Good luck on your decision.
