So there you are unconcious on the ground, having suffered a traumatic injury. Paramedics arrive and want to treat you quickly and also notify your next of kin. Your cellphone, which is close by, has lots of numbers stored in it, but that won’t help the paramedics. Which of those many numbers is your ‘next of kin’?
You can make the paramedic’s job much easier by adding an entry in the contacts list in your cell phone under label "ICE" with the name and phone number of the person that the emergency services should call on your behalf. Read more about this idea, which paramedics are trying to get people to adopt, here and here.
By the way, I’d add an entry in that ICE contact that describes what blood type you are and if you are allergic to any medications.