One of the best and smallest cams I've found is the Mobius action cam. Good quality video and very small. No video screen, but if you need to see anything it captured, just plug it, or the mini-sd card, into a computer.
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I won't post the video, but here's a link to a very thorough (and long) review of it. About $89 on Amazon, less on E-Bay.
Disclaimer: No, I don't work for them or trying to sell anything. I'm just getting ready to pull the trigger on a dash cam myself, and after researching a bunch, this is the one I've settled on.
Question to those who have had the dash cams installed. Can they capture license plate?