In a medical emergency it is important for medical professionals to know as much about you as they can. The Medical ID function of the Health app in iOS 10 can be used to store important information that can then be accessed on the lock screen of your iPhone, such as allergies, blood type, medications and emergency contact information.
Now you may not use the Health app on your iPhone for anything but there is one section that everyone should check out.
I'm using iOS 10 here and you can see my Health app. It's the white icon with the heart in it. I'll go into that and you can see all the things it does like track your activity and such. But if you look at the menu at the bottom, the last item is medical ID. If I go into there I can set various things about me. For instance I can put my birthdate, I can put my blood type. Let me hit the Edit button there and you can see I can go ahead and edit all this stuff. So I can change my birthdate, add medical conditions that I've got, allergies, medications that I'm taking, organ donor, height, weight. All this stuff. I can hit the plus button there and add an emergency contact. All this is part of my medical ID.
You can see at the top of the screen here I've got it selected to Show When Locked. So the idea is that all this information can be in there and if something happens to me, say I'm in an accident or something, they can get my iPhone and get access to this information because I might not be awake to be able to give it to somebody.
So in that kind of situation your iPhone, of course, would be locked. Somebody would come up to it and they would not be able to unlock it. But if they press the Home button again and it comes up with this. There's an emergency button at the bottom left. Hit Emergency and you can make an emergency phone call, like dialing 911.
But also notice it says Medical ID at the bottom left. Hit that and you get all this information. So you can have important information here about allergies or medications and things like that. EMTs and doctors and all should be trained to actually look for this kind of information, not only with iPhones but on android devices and such. So it's very likely that if you put some information here they'll find it and be able to help you better.