A guy hit my car last year, and my then-dashcam-equppage consisted of GoPro 2 Hero cameras mounted in the front and back - one was a gift from the late Don Litten. But they were so much bother that I didn't have either of them installed on the date of the collision. Damnitall!!! Since then, I bought a couple of cameras to replace 'em, and I like the replacements. Not cheap, but some very good points: 64Gb SDHC card capacity (comes with 16Gb), and the oldest data is automagically re-written by new data if the card gets full. The cameras operate on USB power from a converter in the cigarette lighter socket, and come on when the car starts, go off when the ignition's switched off. In other words, they stay put and I don't have to mess with them at all unless and until I have some video I want to review. Here's a link to the product:
I use an Olympus WS-802; apparently discontinued, I believe closest current model is WS-852. That's kind of a mid-range priced device for Olympus, that one's about sixty bucks, but they run up to about two hundred. I've been most satisfied with it, works reliably and does everything I would want it to do. Excellent clarity and sensitivity. I've used it in court hearings quite a lot (where permitted) and never had any trouble picking up what the judge, witness, or prosecutor have said. I use a lanyard-strap that I got for two bucks at Microcenter to carry it around my neck - it's made to be able to be hooked up to such things. Here's a link to the current model:
Incidentally, the links are to BHPhoto a big photo-optics-audio distributor in NY; they don't accept web orders from Friday evening to Saturday evening, because they don't want their computers doing "work" on the Sabbath. I've been doing business with them for years and always very happy with them. They sell a limited supply of riflescopes, red-dots etc. too, by the way.