Car monitors are the best way to know what's going on behind your car. Car monitors will give you a wider view of what is behind you, allowing you to back up safely and without endangering those around your vehicle. Some of the best car monitors are as large as seven inches. Others show you not only what is going on behind your car, but also next to it. Rearview mirrors were the best technology at one time, but now you can install a simple camera in the back of your car and connect it to a digital screen in place of a rearview mirror.