Sensors? Waste of money. Ok down to approx 30cm then you're blind.
And the beeping is soooooo annoying.
I bought a wireless camera off ebay, cost about £50 (colour).
Had to mod the inside of the silver trim above the number plate but the camera fits up inside there a treat (held in place with body filler).
Wire routed through the tailgate to the top then back down the body to the reversing light.
Screen fits just nicely to the underside of the parcel shelf above the mirror (shielded from the front by the shaded area of screen), held on with double sided sticky pads.
Power cable runs onto the parcel shelf, down inside the trim beside the window & into the fusebox, taking power from a spare.
Screen is always in standby with the ignition on & displays the image when reverse gear is selected.
I can see most of the width of my bumper & barely see the tailgate back to about 4 feet. People are amazed when they see me squeeze into parking spaces & my towbar is an inch away from someone's bumper
Only drawback is that a lot of people like to use video senders to transmit a TV signal or security camera signal so you can pick up telly progs or security footage as you drive past. Seems strange to start with but you get used to it.
If I had to do it again I'd possibly consider a camera mounted in an enclosure then surface mounted where the top brake light is, I'd also prefer one that works in near dark conditions. Mine's OK but you have to press buttons to lighten the screen at night, the brakes & reverse light help to illuminate the area.