I have once seen a blind man being loaded into an ambulance after collapsing in the street - the emergency personnel were scanning his dog's ear. I presume he had no ID and they were using the dog's data to find out who he was.

I can think of a lot of musicians who could be easily identified with a chip in their guitar, flute or accordion, as they would hold the thing with a death grip even while in no state to remember their own names and while being carted off to the drunk tank or accident & emergency ward.