All depends on how much you want to spend. Depending on the model Sioverado you have, you could possibly add the factory camera, but they have gone up in price since I looked into it for our '10 Silverado, then for our '13.
As posted, some license plate mounted cameras have a pretty good picture. I just picked up a Peak Auto 4.3" digital wireless system to try to use on the back of the tt. You wire the camera power to the reverse lights to come on when needed. Barely had it out of the package so far as I won't have time to mess with it for a couple weeks.