If you're in an area that doesn't have good WiFi or cell coverage, you could also use an SD WORM card.
http://sandisk.com/business-solutions/sd-worm
Basically, once you write a file to it, it's impossible (in theory) for it to be deleted short of destroying the physical medium itself. It's certainly more expensive than standard flash media, and I'm not sure where to buy one yet, but no matter how many times the thugs impotently pressed "delete" once they've taken your device, they can't delete it.