This should work on most phones. If you dial *3370# your phone will restart with a 50% increase on your battery. Great for if your battery is going to die. It works because all phones have extra battery power. If you do use this code it will recharge your phones extra battery power the next time you charge your phone.
If you need help but dont have a signal, just call 112, it is the world wide emergency number. Your phone will use any avalible satellite to connect your call for help.