Per James:
A lot of folks do that now. We even have a startup company making rear
facing integrated tail lights with camera.

https://www.kickstarter.com/projects...-tail-light-co

Just in case that thing takes off and the day comes for v2.0: I would
buy one in a heartbeat if it could be mounted and forgotten about. i.e.
it could get power from my dynamo.

Even a feature where it got power from my headlight battery and beeped
when voltage dropped below, say, two hours' riding time....

As it is, I've been close to carrying a dash cam a few times, but the
obsessive quality of having to mount it, un-mount it, and charge it have
put me off. But something like the dash cams on my car where I've
almost forgotten they are there? No brainer.... gotta have one.
--
Pete Cresswell