I carry a wallet[1], with a driving licence in an obvious transparent pocket with a piece of paper folded round it with "IN EMERGENCY" written in large friendly letters on the fold. The paper contains useful contact and medical information should, in order of likeliness:
a) My phone b0rks and I need to know barakta's number
b) I'm involved in / witness to an accident, I have a simple piece of paper I can hand to an interested party with contact details on
c) Someone wants to re-unite me with my lost wallet
d) A medic really needs to know my blood group, that I'm allergic to cephalexin or that I understand BSL, but is unable to ask
e) I need to be identified if I'm dead/unconscious/amnesiac
I see no need for special products.
[1] Also containing MONEY, which is likely to be useful for procuring things that would be useful in minor emergencies such as CAKE, tissues, bike parts, battery-powered angle grinders or alternative transportation.