I have a cheapie wireless backup camera that attaches to the license plate screws. I got it with my credit card points. If you had to buy it out right it would be about 30 bucks. If you want a good one you have to spend more money then that. Mine does work but, there is often too much interference and the picture can be hard to see at times too. It's better then nothing but, I suggest spending more money and getting a better one then I did.
Kinda funny though. Because it's wireless I sometimes pickup up the picture from other wireless security cameras as I drive down the road. At one of my local grocery stores I can set in my pickup outside the store and see who is inside before I ever enter the store. lol