This is the fastest way to call the ambulance and open the medical ID: Click the on/off button 5 times. Then, a small menu pops up, containing the following:

Tbh you NEED a medical ID.

If you just randomly collapse to the ground and you don't have anything like a passport or whatever with you and nobody knows who you are, the people trying to identify you have a problem. For that, you have the medical ID: It shows your name, age, height, weight, allergies etc(if you write it in there).

If you don't have a medical ID yet: Go to contacts, Edit yourself and click "add medical ID"(at the bottom).

Thank you.