It's on my phone, and other relatives....
Let me tell you a story (real life) where the ICE thing would have cut down nearly half a day getting in touch with someone to comfort a young child that lost a parent in a MVA.
Called to scene at about 0230 hours. Dead guy in road that had been run over after being ejected from stalled vehicle. Child sees Dad in middle of road. Not good...
Child transported to nearest hospital for treatment of any injuries before I got there. Family on way to another state about 1600 miles away, no home phone, cell phone has virtually no phone numbers in it. Only thing available to go on is an old address book the child had. Phone numbers in it were useless - "number is not in service" messages when trying to get ahold of the other parent.
I now have a young child that's old enough to put two and two together to come up with 3.76, or, pretty well knowing Daddy's dead, but no one can tell him/her until I get the other parent or a family member/trusted family friend there for emotional support and guardianship. Sucks to be both of us at this point.
It wasn't until nearly 10 hours later with some decent detective work and verbally making a phone company supervisor feel as guilty as a dog that just piddled on the carpet before he gave me the info I needed without a warrant or other such horsecrap. All I needed was phone calls to a certain area code off a calling card to narrow it down. "Imagine, sir, a child has been here for 10 hours without knowing where the other parent is, or if Daddy's actually dead. Now, close your eyes, and imagine that's your son/daughter that's here."
Dead silence. "What area code did you need?"
Had the other parent on the phone within 5 phone calls.
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ICE on the phone in this case? A quick call to that number, or in my cases, have the police or local EOC (911 center) run their protocols and get the info from the phone companies on an address the phone is listed under. Police and/or my agency goes out to that addy for further investigation/notifications. I don't do notifications over the phone unless it's the absolute last resort. You just don't want to see me and a cop show up at your house at 0200 hours...
It may not have provided instantaneous communication with that party, but voicemail is a wonderful thing when the phone isn't answered right away.
Bottom line - in my line (and previous line) of work, there are times that it would be invaluable in trying to get in touch with the next of kin.
As a former EMT, I can count on the stump of one hand the times I've dug into someone's wallet for medical information. It's just not done in probably 99.9% of squads. Phone numbers on slips of paper also work, but generally when the SHTF, it's not looked at until you're in ICU recovering or the coroner has been called.
Personally, ICE is in my phone. I also like the ICE 2, ICE 3 idea mentioned earlier. Should an honest person find it, you might just get it back quicker without all the calls to Japan, China and Sri-Lanka on it, too....
Just my $0.02 worth....