Medical ID Cards

Carrying a medical ID card is something that should be more common. If everyone carried one, lives would surely be saved. Medical professionals would be able to find out quickly and easily if someone has any conditions that should be taken in consideration before treatment. If everyone carried one, even if they have no known conditions, that information could be just as useful.
 
Modern Technology

Members of the armed forces wear 'dog tags' that carry their information, so it is not a new idea. As with the tags, if everyone carried a card in their purse or wallet, anyone trying to help in an emergency would instantly know where to look for information. If you are incapacitated for whatever reason and cannot speak for yourself, a card with your medical information could save your life.
It could be updated with information about immunisations for keen travellers, or carry details of your next of kin and their contact details. For security, some information could be stored on a chip, available only to those with appropriate readers – an ambulance crew, for example.
 
Cards Are Not Compulsory

There is no obligation to carry a medical card, but you never know when you might need one. Many people used to carry donor cards, and medics were used to looking for them, so this could be an extension of that. Make sure your friends and family know that you carry a card so that until such time as it does become compulsory, if the worst should happen you're covered. A little card could give you a lot of peace of mind.