FWIW, I fitted a reversing camera to the car. It was limited in success. The problems were the viewing angle was too small and the display was only 2.5" and not bright enough.
However I subsequently bought:-
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with a 7" screen and wider viewing angle. I haven't yet fitted this, but the reviews are good so some time in the future I'll get around to fitting it. It just hasn't made it up the jobs list yet. Bumper sensors are useful but I wouldn't bother to fit them.