In view of the recent events in London, East Anglian Ambulance Service have launched a national "In case of Emergency (ICE)" campaign, with the support of Falklands war hero Simon Weston and in association with Vodafone's annual life savers award.
The idea is that you store the word "ICE" in your mobile phone address book, and against it enter the number of the person you would want to be contacted "In Case of Emergency".
In an emergency situation, ambulance and hospital staff will then be able to quickly find out who your next of kin are and be able to contact them. It's as simple as that, and for more than one contact name you can use ICE1, ICE2, ICE3 etc.
There's more info on the East Anglian Ambulance website.