I recently had some money left on an Amazon gift card and fancied using one. Anyway I basically bought one of the cheapest possible one I could find. The model is GS8000L and comes from various manufacturers and cost me £13.50 but had to buy a separate 32GB SD card at around £7.
I posted a short loop of how it performs. It is advertised as full HD but I found that it seemed to work too hard in that mode and works best at 720p, plus you get near 4 hours on the SD card. Also bear in mind it is in my Corrado G60 with near non-existent suspension. I fitted an another cigarette lighter socket hooked up to a 12v ignition feed behind the dash and fed the wire up the A-pillar and along the head lining so it begins to record once power is fed to it. The internal battery is quite poor but no big deal really. Motion stability is turned off. Sound is quite poor, seems to pick up the noise of the lense but overall a decent bit of kit for the money. It is quite small and compact too.
https://youtu.be/1ZZB-B4W3ws