Emergency SOS on your phone: the setup, and the limits.

On an iPhone

Everything lives in two places. Settings, then Emergency SOS, is where you decide how the call is triggered: holding the side button with a volume button, or pressing the side button five times. Turn on the countdown sound unless you have a reason not to, since it is what stops accidental calls.

The second place is the Health app, under Medical ID. Fill in the emergency contacts, blood group, allergies and treatments, then allow it to be shown on the lock screen. That last switch is the whole point: it lets a stranger or a paramedic reach your people without your passcode.

On Android

The wording moves between manufacturers, but the destination is the same: Settings, then Safety and emergency, or the Personal Safety app on Pixel devices. There you add emergency contacts, write the emergency information shown on the lock screen, and switch on the shortcut, usually pressing the power button five times.

Turn on emergency sharing while you are there. It sends your location to your chosen contacts when an emergency call goes out, which is the difference between someone knowing and someone being able to come.

Before you test either shortcut, know the way out: on both systems a countdown comes before the call, and Android can require a three second touch and hold before anything starts. If a call does connect anyway, do not hang up: tell the operator it was accidental and that you do not need help.

• Emergency contacts: two or three, told in advance
• Emergency information visible on the lock screen
• The shortcut settings checked once, without setting off a call

What it does well

Once set up, one gesture calls the local emergency number, passes your position to the operator and warns the people you listed. In the European Union that number is 112, from any phone, in every member state, including with no credit.

The location part is the underrated half. Emergency services in most European countries receive a far more precise position from the handset than from a spoken description, and it arrives before you have finished a sentence.

The three moments it cannot cover

First, the phone has to be in your hand. In a coat pocket, at the bottom of a bag or on a table two metres away, the shortcut may as well not exist. Second, the gesture needs enough calm and enough grip: a five press sequence is easy at home and much less easy when your hands are shaking. Third, a flat battery ends the entire chain.

This is the honest limit of any phone based safety plan: it puts a screen in the critical path. Something on your keyring that fires an alarm and an alert without unlocking anything removes that step, and the two work well together rather than replacing each other.

• How it works

Any questions?