Given the tip on setting up an android handset, so that a number would scroll along a locked handset, from a Paramedic.
Don't carry one with me, but I do have a mobile and it has been used, by those in the ambulance service to prove who I was. On more than one occasion. If they are called to attend, then I'm usually out of it and unable to answer.
I'm also aware that both the ambulance service and police will seek some means of identifying a person incable of giving a response. A small laminated, printed card, containing my details, Drs details, current medication and known allergies is carried. As they will search for any ID.
This was another "Urban Myth" that has since been laid to rest.
The lock screen tip works for any phone with a lock screen that is personalised, whether it be Android or IOS
Personally I carry a "RoadID" wrist band and have a cheap key ring tag that gives my name, and my wife's mobile number attached to the frame