I use cheap dashcams in the cars. Normally pay less than £100 but quality is OK-ish. Have a look at the TechMoan youtube channel/website.
my mate has a Roadhawk Dc-2 and used it for a few years when he's out in his lotus RoadHawk DC-2 Dash Cam I've also used dogcams a few times and they are very good
I have one which I got primarily for the wife, but I also use for crash reconstruction. First time my wife went ona long(ish) journey she had someone reverse into her and then try to claim that she had driven into the back. They also said that they were injured (yeah right). Fortunately, no damage to the wifes car, but as the other driver started going on a rant at the wife, she simply pointed to the camera on the dash which was recording everything. I saw the footage and the look on the other driver was brilliant. Not only was registration number as clear as daylight, the drivers face was there for all to see, confirmed that there were no passengers, but most importantly it proved that the driver reversed into her and not the other way round. Driver was back in his car and drove off in a panic and like a maniac What we have is only a cheap item we brought of Ebay for about £25 (new) but it is High Def and all the bels and whistles and I use it all the time for work, but that one incident was enough to justify the cost. Footage was passed to the Police which they can use as evidence. But........... Also bear in mind that it can also work against you if you drive like a knob and forget to wipe the footage at the end of your journey, or.... you are involved in a crash and your actions are contributory and you are unable to wipe the damming evidence in time for whatever reason.
I have one too as I keep coming across idiots every time I head to the office. I have one of those £25 eBay ones. Got a spare too which I may sell. Best bit is that it loops the recordings and you can always remove the sd card if you cause the crash
Mates used his for about 18 months and very happy with it but I had been looking also and for the money 1080P HD 170° 2.7" LCD Car Dash DVR Video Camera Cam Recorder Night Vision HDMI | eBay 1080P 170° 2.7" HD TFT LCD Car Dash Camera Video DVR Cam Recorder Night Vision | eBay
We use a Blackvue in the Wife's Merc and I use a cheap £50 jobbie in the Van. The Van one just records in HD with sound where as the Blackvue gives full Geotagging speed etc and also plays back via a split screen showing your vehicle position on a live Google Maps Screen. Blackvue 2014 In Car Camera Range - Official UK/EU Stock - Blackvue DR600GW-HD, DR650GW - 2CH, DR550GW-2CH - Dash Cameras UK - Blackvue Sport SC500 Action Camera
I use the Blackvue 650 and it's very good. Before this I had another which was cheaper but the motion detection was not great when in car park mode but this is much better. Quality is good for both front and back. Also filmed me at brands the other day as they made me take me gopro down.