All you need to do is store the number of a contact person or persons who should be contacted during emergency as "ICE" (meaning In Case of Emergency) on your mobile phone.
In an emergency situation, Emergency Service personnel and hospital staff would then be able to quickly contact your next of kin, by simply dialing the number stored as "ICE".
For more than one contact name simply enter ICE1, ICE2 and ICE3 etc.