If you - or your child - is in an accident would the emergency services be able to find the number of the correct person to ring on your mobile phone? Some of us store numbers under home, or parents (one of my friends stores her under "Oldies"!) but if we just have names it could take ages to reach the appropriate person.
For that reason, a paramedic thought up the idea of the ICE campaign - in case of emergency. If everyone has a number keyed in for ICE it could save vital time. Emergency service personnel and hospital staff would be able to quickly contact the right person by simply dialling the number you have stored as "ICE" and if you have more than one contact for emergencies store them as ICE 1, ICE 2 and so on.
If your children don't have a mobile phone let them always carry a card with your name and contact details. I did this whenever my daughter was taken out by anyone else. It occured to me that if there was an accident, she would be assumed to be the daughter of the adult or adults she was with. To this day I think my daughter still carries my business card in her purse!