Very happy with this setup. I boght this eBay G300B rearview camera DVR off FleaBay for $60.
I've got it set to 1080p, 5-minute loop recording on a 32gb SanDisk microSD card. Works great. I chopped off the cigarette lighter plug because I have no intention of manually plugging/unplugging it to get the camera started and no desire to occupy an outlet necessarily (and in an ugly way).
So figured out that the unit uses 5vdc not 12. I bought a cheap transformer off Amazon for $8, soldered it on where the plug was, and it works great! The only hardware beef I have is that the positive and negative wires inside the cabling are ridiculously flimsy - maybe 26 gauge I'm guessing. It's literally like 4 tiny strands on each and pretty easy to screw up. I soldered everything and used lots of tape to keep it stable. Oh well. I wasn't about to spend $2,000 on a LEO Silent Witness or whatever.
Sample video outtakes to follow.