Too be quite clear from above, the HD CCD in my dash cam is a smidge less than the diameter of a 1911 recoil spring bushing. It uses a microSD card for storage (the 32GB card I have will store about 40-50 hours of video in 5 minute increments).
What that suggests to me is that a recoil spring guide video camera is possible, technologically. A grip-based style like the Crimson Trace ones would seem equally likely. If we "stole" a concept off the Holosun sights, a motion-baed "on" switch and modern battery-use tech would make such a device relatively "low fuss."
Now, for "action" gun matches, this would be really cool--a "guns's eye view." For the everyday, well, that can of worms we have touched on above.
Would make for an excellent training aid, though--did you sweep yourself or others, well, here's the proof of it or not. (Come to think of it, might solve some of the arguing about "breaking the 170/180" at some matches, too . . . )