This free location app could save your life - and now emergency service providers are using it to locate people.

what3words uses three words to give location data.

The technology can accurately locate a person's whereabouts, which could help emergency services if you don't know where you are.

So far Thames Valley Air ambulance has asked people to use the app as it can precisely indicate where a patient is if they are in a remote area or somewhere with no obvious address or landmarks.

It works like this, as explained by the app developers:

"what3words is a really simple way to talk about location.

"We have assigned each 3m square in the world a unique 3 word address that will never change.

"For example ///filled.count.soap marks the exact entrance to what3words’ London headquarters.

"3 word addresses are easy to say and share, and are as accurate as GPS coordinates.

"Our vision is to become a global standard for communicating location.

"People use what3words to find their tents at festivals, navigate to B&Bs, and to direct emergency services to the right place."