A startup called Lifesquare has a nifty idea: Put your vital life-saving information (medicines, allergies, conditions, etc.) into a QR code, put that on a sticker, wear the sticker (or put it on your wallet or bike helmet or whatever). In an emergency, paramedics could scan the code and offer you the best assistance possible.
Cons: You hand your medical information over to a private company.
Lifesquare has partnered with Marin County, CA for a pilot program. Think they’d make mine as a face tattoo? Maybe that's not such a hot idea, in case my medicines ever changed... but I can't help thinking I might want something a little more sturdy than a "sticker" to weather a car accident.