Non veni pacem mittere, sed gladium.
I have one for forward recording and I'm gonna get one for the back window as well. That way I'll be covered fore and aft.
These things live a brutal life: make sure to regularly pop the memory card to make sure it's still recording. I failed to do that and didn't have the video when I needed it...camera display was still working, but as evidenced by the last date stamp, the recording part died a couple months before my wife got bumped.
I have a cheap one on my front windshield- only $20 online. It takes good clear videos but they're a bit jerky on playback. Good enough though. It plugs into the cigarette lighter so I never have to recharge it. Want one for the rear too, but I'll have to find a source of power to run it. Cheap insurance if somebody runs into me!