I had a thought the other day that perhaps the best place to keep medical records is in implanted microchips. That way, instead of looking for an alert bracelet for allergies, testing for blood types or asking the family about organ donation, doctors can just read the microchip. Of course it's not as fail-safe as a bracelet (what if your electronic reader gizmo dies?), the family may have different opinions on organ donation and there's always the possibility of data corruption. Also, securing data that is always carried on you to broadcast on demand is pretty hard to secure. So it seems unlikely that anything like this will ever take off, but it's interesting to think about.
Mokalus of Borg
PS - You could store a fair bit of info there if you wanted.
PPS - Maybe it could work for some things.