I have combined both my own morbid sense of humor, and the concern of family members. On the back and side of my helmet is written: "If found w/o rider please call [My cell phone] If found on rider please call [A Different number]." THis has served two purposes, my ICE is on the one item I am not seperated, and when a girl askes who the the other number is I can tell her it is my mom. It works wonders.
Dog tags are a problem outside the US as I do not want to be ID'd as a US Storm Trooper. Depending on my travels I may leave them at home.
The problem is that the information has to be Durable and Available (Thus the phone numbers are on two places on my helmet).
I will probaly record critical medical information in the same format found on Shot Records and Passports, on a metal tag that is stored on or in my boot.