I have two Nextbase 402G cams fitted, which are a few years old now, but have performed faultlessly.
As others have said, it is important to go for the HD version, as they are useless if you can't read a number plate.
I started with just the front camera, but Sod's law intervened and my last bump was a rear end shunt, fortunately the driver admitted responsibility, so there was no problem, but the second camera was added shortly after, just in case!