I have ICE 1 husband and ICE 2 parents on my mobile.
I used to carry one of those SOS talisman pendants on me when I did alot of horse riding but I've lost it.
We have wristband tags for my young son for when we are out and about, it has a space for our mobile numbers to go on.
Carry a donor card, that has contact numbers on.
I've worn a medical alert bracelet since I was 7 years old, it has code on the bottom so if someone calls the toll free number they can get all my emergency information including my doctor's name.
The one I wear is calle d"Medic Alert" and they come in stainless stee and 14kt gold. But you can engrave information on the back of your watch of a dog tag style pendent that you can wear under your clothes.
There are a few low-cost products on the market now designed to help with this. My family have wristbands, keyrings and dogtags from www.iD-Everywhere.com
Each product has a unique code and you put in any information you want to on their database. I have our emergency contact details on it, but when we go abroad, I also put in our passport details, itinery, insurance details. You can add medical details too.
You can buy dog tags and get them engraved. Also some of my friends who have say life threatening conditions like diabetes, tattoo on there wrist or chest saying, I have diabetes my NHS # is ....., also
make sure you always carry your driving license or something around. My mums partner had a necklace saying he has a heart value condition or something and forever wore it. Or wear like a hospital wrist band, its plastic you can write on with biro and it never fades.