Accidents happen far more than you think they do. Each year approximately 450,000 of us are taken to hospitals unconscious and without identification.Road ID was launched by a father and son who realized that how common it is to leave your house to work out without ID. They came up with these laser engraved plaques that can be worn on your wrist, ankle or shoe.
Another take on having emergency contact info easily assessable is to program "I.C.E." (In Case of Emergency) numbers in your mobile phone. The idea was launched by a paramedic in the U.K. after the July 2005 Terrorist Bombings in London, were EMS providers were having trouble locating emergency contact information for disaster victims -- it's simple to do, just select those you would want to first be contacted and label them under "ICE SISTER", "ICE DAD", "ICE DOCTOR" etc. and they recommend you have an ICE sticker on the back of your phone so the EMS knows what to look up right away.
And in this smart phone era, there is a 'smart-ICE' iPhone application (for $.99)
Being the safety freak that I am and having worked with the Office of Emergency Management (OEM), I am always weary of anything electronic in the event of an emergency (esp. after being in NY during the black out). So last year after researching what to do in an evacuation, I made these little ICE cards to be kept in your wallet (below).
Once I figure out how how to post a PDF I'll make them available.