(not cyclocross race related I know, but for road training)
I highly recommend this podcast, interviewing Josh Zisson an attorney in Boston, with his own practice specializing in bike law: http://www.thepodcasthost.com/thesprocketpodcast/2012/01/08/447/
(and see his web-site: http://bikesafeboston.com/ ).
Josh recommends that all cyclists use 2 cheap "police body camera" style video recorders; with one facing front and one facing backwards, whenever they ride. These simple flash memory video cameras can record a days worth of video, and you would simply strap it to your helmet, jacket, and/or backpack; and use it as a daily commute recorder. If nothing happened that day you could erase the memory (or allow the camera to continuously over-write the memory) and go about your day. However if a car hits you, you will have it all recorded.
Josh Zisson mentions that this video evidence is key in getting a fair settlement from the motorist's insurance company to cover your rehabilitation costs.
SJCAM M10 is a budget version, and the Rideye camera records a continuous loop and the batteries last 15 hours.
the thing with infinite loop recording is that it needs to stop at the right time. If you forget to stop it in the heat of the moment or worse (incapacitated) you get the last hour of arguing or paramedics...