Well, OK, those are issues, but not necessarily all insurmountable, and chips have been and are implanted in humans. I'm also not suggesting this is something that should replace more conventional methods, but I think it has many significant advantages.

As for bracelets or necklaces - bracelets are *definitely* visible and I don't think a necklace would suit me, and would still be visible a lot of the time.

I still think chips increase privacy over any sort of external tag you have to carry. Anyway, my real gripe is that there isn't a decent solution to the problem MedicAlert tags aim to solve and so I just rely on a card in my wallet.