Therefore it's important to carry your mobile with you at all times. I used to leave the mobile in the Land rover as I believed there was no point taking it with me due to no service, I always carry it with me now.
I have never tested the following, but I recently got a list of "things your mobile phone can do".
The emergency number worldwide for Mobile is 112. If you are out of service area this number will search for existing network to establish emergency number for you. It works with locked keyboard. (Looks like 999 does that as well, Wnw.).
If you lock your keys in the car and the car has remote unlocking. If you have your mobile and the spare keys are at home, phone home and, hopefully, get someone at home to pick up your spare keys. hold your mobile close to your car whilst getting the person at home to press the unlock part of the spare key whilst holding it close to their mobile. Your car will unlock.
If your mobile battery is low press *3370# to activate reserve.
If you are alone at an ATM and become enforced by a criminal to withdraw cash, you can notify the police by putting in your PIN number in reverse. The ATM recognises your PIN number is backwards, to that on your card. The ATM will give you your money but will send the police to that location.
When in Rome, do as the Romans do.