iOS has an Emergency SOS feature which calls the emergency services fast, and can alert your loved ones to the emergency.
Using it works slightly differently depending on the device you have.
If you’ve got a newer iPhone with no Home button, press and hold the Side button and either of the Volume buttons until the slide to power off screen appears. (Be aware that if you keep holding the Side and Volume buttons even longer, a loud alarm will sound.)
If you have an older device with a Home button, quickly press the Power button five times instead.
Then, swipe the Emergency SOS slider to automatically call the default emergency services in your country.
It’s worth noting that using this feature deactivates Touch ID / Face ID on next login, requiring the user’s passcode instead.
If you have defined any emergency contacts in the Medical ID section of the Health app, they will automatically be sent a text with your current location when the call ends.