^this.

The *only* reason you need a tag is if you are unconscious, unresponsive, or not able to communicate accurately (i.e. think some level of concussion). So what the tag needs is your name, the phone number of next of kin and some way to get your critical medical information to medical personnel as fast as possible to render life saving aid. After that, there's plenty of time to figure out who you are and the best way to do that is for the medial team to get in touch with your next of kin. Putting all the rest of the ID information like passport, etc.. is pretty much worthless and probably more of a security risk in the event you lose your bracelet/tag.