After my memory-affecting concussion this spring, my wife is ordering me a RoadID. I've got a license with contact info that I always have in a jersey pocket, but you never know if that will stay with you either. The license allowed my training partners to call my wife when I was experiencing the amnesia.

Serious crap can happen, so having some way to contact a responder is a good thing. Doesn't have to be a RoadID, but they seem pretty convenient and high quality.