A while back, a thread talked about using dog tags for ID. Heck, I use 'em.
Well, how about an electronic dog tag:
This puppy stores 40 lines of info for 40 bucks. Looks like each line is 10 characters long, so that's 400 characters. That should be enough for ID, contact data & medical brief. Works is 6 languages, so could be useful for travelers.