My info is outdated. 5 years ago my wife had a GMC Envoy XL. Dealer wanted $750 to install the backup sensors. I had a aftermarket shop due it for $225. Watching my wife swing that thing around parallel parking was a thing of beauty. They are worth every penny. Our new expy has the camera in the rearview mirror, and the sensors, and it is awesome.

Note: The GMC had the sensors triggered to the reverse lights. When you remotely unluck the doors, the convenience lighting lit the reverse lights, so while you loaded the back of the car the sensors would be beeping, a little annoying. The Expy does not light the reverse lights when you unluck with the remote, so no beeping. Though the sensors are still powered from the reverse lights.