I saw this neat little flash drive bracelet at the pharmacy and rang up the EMTs and a couple hospitals to ask if this would work (having tons of medical conditions and all,) what they said amazed me a bit.
The hospitals, in particular, were adamantly against them--they didn't want any chance of corrupting their computers, even if that information could be lifesaving (the EMTs backed the hospitals up, including that they rarely have access to a USB drive right away and when there's an emergency, they're just going to start doing something fast.)
So I said to the EMTs, "What medical I.D. do you look for/use?" They said the best/preferred place to wear medical I.D. is as a bracelet (I imagine b/c they usually start an I.V. almost immediately.) Then they said to put as much information as you possibly can on those little metal charms--latex-allergy, immunocompromised, Sjogren's, Paradoxical Vocal Cord Dysfunction,...any medicines, etc. (I'm envisioning a charm bracelet, lol.)
Honestly, I was kind of surprised by the answers, esp. as a flash drive could store other essentials, too, such as contact info, DNR, will, living will or any religious restrictions on medical care...but everyone's saying "Nope" for now.