If you have a relatively new car, it probably turns on the back-facing camera when you put the car in reverse, letting you see, without turning your head like an owl or like in The Exorcism, what's behind you. This not only is a terrific safety feature, it's a big help when parking. If you don't have one that came with the car, you can get a kit to install one, ranging in price from under $50 up to a few hundred dollars. Our Automotive Research Team (ART) started looking at them and got such a headache it just stopped. There are a lot of features to consider: most clip onto the license plate, but some need a hole drilled in the car to run a wire to the trunk for a power supply, while others don't running on batteries; the blue tooth screens vary in size and features; battery life varies and is dependent on a bunch of factors; some will transmit the picture to your phone, others won't; etc. etc. etc. While ART gave up, it might be wise not to. The good new is because they are blue tooth based, you don't need to run wires from the camera to the display.