Ive never installed one but im really into wiring you could tap it into your cigaret lighter and add a toggel switch. but as far as the making it come on when you reverse? i guess you could try to rig some relay switch but im not sure how great that would work. if anything you can just put a switch and flip it everytime you put it in R. sorry i cant help more

Nick

 

Tap your reverse light wiring at the socket area. This will give you power when you put the it in reverse.