Since your phone, numbers, contacts, and texts are now deemed "open communication" I suggest keeping a passcode on your phone for security.
The police no longer need a search warrant to view text messages and such.
People v. Diaz -California: http://www.askthejudge.info/can-a-po...-messages/186/
Nothing wrong with a 3 x 5 card in your wallet/purse, maybe in your phone case, or your glove compartment. I believe in ICE notifications but not on an unlocked phone.
I especially believe it is needed if you have children, elderly parents/relatives, or pets that rely on you to come home. If they are dependent on you and you are incapacitated that somebody know that help is needed at home as well.
It doesn't take much and you certainly don't need a "phone app" to do it.