When you’re in an emergency, you may not have time to enter your passcode, click on the call app, and enter 911. Apple has made things easier in an emergency by creating a feature that allows you to call your local emergency number while your phone is locked. This also helps if you're traveling because you may not know the emergency number for that area.
This feature is slightly different depending on the model of iPhone you have. For example, the iPhone 7 requires you to click the lock button 5 times (or 3 times in India). The iPhone 8, 8 plus, or X requires that you hold down the lock button and one of the volume buttons.
After the emergency call is made to emergency services, your phone can send out texts including your location to emergency contacts such as your parents. This feature is optional. You can also add medical information that can be accessed by medical professionals.
To add this information, click on the Health app (white square with a heart in the corner – on every iPhone). It will then prompt you to enter the information for your contacts and your health information when you click "Create Medical ID".
You can also use this feature from you Apple Watch but your watch either needs to be connected to Wi-Fi or your iPhone needs to be nearby. Similar to your iPhone, the call is made by holding down the button on your watch and sliding the “Emergency SOS” button.
You can, of course, turn this feature off by going into your settings, clicking on “Emergency SOS” and clicking “Hold to Auto Call”.