ICE stands for "In Case of Emergency".

By adopting the ICE advice, your mobile phone will help the rescue services quickly contact a relative or friend — which could be vital in a life or death situation. It only takes a few seconds to do, and could easily help save your life. Simply select a new contact in your phone book, enter "ICE" and enter the number of the person you wish to be contacted in case of an emergency.

More details here

Do it right now. Take out your cellphone, and put your ICE numbers in it.