Now there's an app that lets your family or friends track your journey and will call for help automatically if it senses you're in trouble.

现在有一款应用能让家人或朋友了解你的旅途足迹，当感应到你遇到危险时，自动求救。

Called Companion, the main feature that distinguishes it from other tracking and GPS apps, such as Apple's Find My Friends, is its 'Are you OK?' button.

Before setting off on a journey, users input¹ their starting point, their destination and a designated 'companion'.

This can be anyone in the user's contacts book, and they don't need to have the app installed.

The 'companion' can then track the phone's GPS to see where their loved one is at any time, while the app will periodically show a button on the user's home screen asking 'Are you OK?'

If they don't press the button within 15 seconds, the companion is sent an alert.

The user is also given the option to call the police from within the app.

Elsewhere, the app can detect if a person has been running, or headphones have been removed from the audio jack² suggesting the phone has been dropped, for example.

If this happens, the 'Are you OK?' button appears and the 15-second countdown starts automatically.

Companion is free for iOS and Android devices and users need to enter their mobile number to sign up to the service.