If you want to go cheap, I used this $15
camera from Amazon, a $20, 5" TFT monitor from eBay, and a $10 20' RCA cable to connect the two for my TV. I'm sure you could use the same set up with a longer RCA cable and wire the monitor and camera to a switch instead of the back-up lights. I've had the cheapie camera for for 2 years now and it's still holding up well but either the camera or monitor will stop working when it's extremely cold outside.