I wear a SOS Talisman medallion. It sounds a bit like Child Safety ID bands, but I have the option of wearing it as a pendant and it's for adults too. It also has a l-o-n-g (22.5 cm or 9") strip of paper inside which concertinas up to fit, and which has ALL my medical info on it - what medications I take, what I'm allergic to (could fill a book) and contact phone numbers for family, doctor, specialist. Blood group, diagnosis, immunisations and dates, past surgeries, hospital file numbers - everything. Even emergency treatment advice. It all fits on this strip of paper (husband has customised a computer page so he can use a smaller typeface and so easily update the info, print out a new strip and carefully cut it out to fit it in). The paper strip is easily legible with lots of useful information. The medallion has a r-u-b-b-e-r gasket inside to keep the paper completely dry. I've never had a problem with the paper getting wet and I wear the thing ALWAYS - swimming, showering, etc. I only ever had to take it off in a hot sauna, because ANYTHING metal next to your skin will burn. Another sauna option could have been to cover it with tape.
It can be purchased as a bracelet or pendant, comes in gold, silver or sterling steel. It can only be bought via the website, but I've worn one for years. Lost it only a couple of months ago (I was wearing it on long leather thong, it came off when I pulled a shirt over my head, so it's somewhere in the house - I'll pass it on to husband or difficult child 3 when I find it).
I did find with my previous one (which I bought in 1978) that medicos don't recognise what it is very quickly, so this time I bought one with a caduceus on the back (that's one of those medical symbols - snake on a staff - symbol of Greek god Hermes and also the Greek god of healing, Asclepius).
It's come in handy for us a number of times. There have been a few times when I've been in hospital but unable to remember or communicate medical info, and they've got out the paper strip to write the details into the file. husband can remember only some of the stuff, but on the paper strip it's saved a lot of time and hassle.
Here's the website -
http://www.sostalisman.co.uk/
I just remembered - I'm on my third since 1978. The first one was gold-plated and we engraved the back with "unscrew for medical history". Unfortunately, you shouldn't engrave gold-plated stuff. And I was just too rough on the thing, the gold layer began to peel off after the engraving insult and it began to look worn and less attractive after about ten years' constant wear. Then we bought a stainless steel one and it was marvellous (until I misplaced it a couple of months ago). I love my new one, I especially feel a bit more secure with the caduceus on it.
Back in early 1978 when I began to develop allergies, I had bought a silver disc medallion and had it engraved "allergic to penicillin." Then a few months later, I developed another allergy. We added that as well. Then when a third allergy (to a drug with a long name) came along, we were running out of space and challenging the skills of even the most talented engraver. With what I use now, I can update when I need to without getting a new medallion or finding a skilled engraver and I also know it's going to be legible.
Whatever you choose - get one with a paper strip that you can update. And before you write on the paper strip, scan it or photocopy it so you can duplicate a master on your computer. Then you can type your text in any time you need to modify it, and simply print another copy.
Good luck!
Marg
A PS from Marg's Man
The SOS Talisman is good because it DOES NOT rely on being kept up to date in a centralised database.
Computers crash; your subscription expires; the phone is engaged; it's needde during a disaster and the system is overwhelmed, etc, etc, etc.
This method means you keep it up to date AND it is with you when it is needed.
It also 'works' wherever you are, whether in a remote location such as the Australian outback, the wilds of Canada, the deserts of Nevada.
Marg's Man