In this video we walk through the SOS emergency feature of IOS 11. When it is set up, pressing the lock screen button 5 times rapidly will activate the feature. When you make a call with SOS, your iPhone automatically calls the local emergency number. In some countries and regions, you might need to choose the service that you need. For example, in China you can choose police, fire, or ambulance.
You can also add emergency contacts. After an emergency call ends, your iPhone alerts your emergency contacts with a text message, unless you choose to cancel. Your iPhone sends them your current location, and, for a period of time after you enter SOS mode, it sends updates to your emergency contacts when your location changes.