I've been using a Roadhawk in the car for a few years, but the quality of the video wasn't really good enough to use it for documentation with OSM.
In Dec 2011 I then bought a DOD GS-600, which has HD quality video. So this little gadget records in 1080p (or 720p, if you want to save a bit space), in whatever interval you set it (mine is set at 15 minutes) and when the microSD (in my case 32 GB, the maximum) is full, it starts overwriting the oldest files.
It also has a build in gyro and gps.
On top of this, it logs GPStracks in it's own proprietary format, consisting of date, time, latitude, longitude, x, y, z
X, Y, Z and movement data based on the gyro and thus not too interesting.
I used gpsbabels xcsv function to convert the file to gpx tracks.
The style file looks like this: dod_gs.style
The command to convert it then is: /usr/bin/gpsbabel -i xcsv,style=dod_gs.style -f "$1" -x transform,trk=wpt -o gpx -F "$1.gpx"
A resulting trace would be: Todays trace
And here is the video from the last leg of that trace: Athlone drive
Signs can be clearly enough identified and used for documentation. A lot of features can be identified. All in all, fairly usable.
The GPS is pretty accurate, as the camera sits in the windscreen at the very top.