I installed a backup cam in my 07. I used the reverse light to power the camera and monitor but also installed a diode in the power source from the reverse light. The video signal cable which goes from the camera to the monitor had a 3rd wire for power to turn on the monitor when the reverse light turns on. Grounds of course are common. This works to turn on the camera and the monitor when in reverse. But I wanted a switch on the dash so I could turn the system on so I could see behind the car when not in reverse. So at the monitor end, I found unswitched power from the power outlet and put a diode in that circuit feeding a new dash switch to then feed the power wire coming from the camera. That way, when I turn the switch on when not in reverse, the camera and monitor activate and I can see behind the car. The 2 diodes prevent this power from turning on the reverse light when the switch is on and prevents the reverse light power from paralleling the power outlet circuit. Without the diodes, I would be paralleling 2 power sources when in reverse and the switch is on but I don't run with the switch turned on very much and of course not in reverse very much and the diodes prevent backfeeding. This works great for me and I really like seeing behind the car when not in reverse (I have a trailer hitch and use it for a bike rack so I can see that all is fine behind the car and the straps are still there). I tried a wireless camera but found there was lots of interference from other cars using those lane drift sensor alarms and the image would distort badly. Direct wired is much clearer.