Video Cameras as rear-view on vehicles

Since we bought our van several years back I’ve been interested in getting one of those little video cameras that go on the back, with a little monitor up front that are used instead of rear-view mirrors. As the van has approximately zero rear-view through the mirror, this would be amazingly wonderful.

I’m nowhere near being able to afford it at the moment, but something I was looking at online reminded me of it and my interest and curiosity was revived so I figured I’d ask you-all.

Does anyone have this setup? How good is it? How well does it work in the dark? How expensive is it?

My father has a video system on his motorhome. One camera at each bumper end and one mounted centrally above the back window. It makes backing it a breeze.