Emergency responders have been doing this for years.
In your cell phone contact base, list ICE....In Case of Emergency. Then list first name and cell number(s) of who you would want notified in case of emergency!
This is for first responders (police, fire, emt), to make emergency contact with whoever you have listed.
If they cannot locate any other form of identification, or must notify someone in an emergency case, they will check a cell phone for ICE.