Technology pioneered by the US military during the Cold War is being trialled in Surrey in a new drive to keep vulnerable local people safe.

Global Positioning System (GPS), now widely found in car sat navs and aircraft, is being used to stop people with dementia getting lost in the county.

A watch is being trialled with a built-in tracking system that allows the wearer’s location to be accurately pinpointed on a mobile phone or computer.

Relatives go online to see a map with a marker showing where the wearer is, and they can even set up a designated ‘safe’ area so that if the person strays beyond those boundaries, an alert is triggered.

Further trials of similar devices for people with dementia and learning disabilities are being planned for the Mole Valley, Elmbridge and Runnymede areas.

The first person to use the watch, supplied by Finnish company Everon, is a cycling mad father-of-two, who is in the early stages of dementia.

It has allowed the 60-year-old to continue doing the sport he loves while his family know that if he becomes confused or disorientated – one of the most common concerns for relatives of people with dementia – he can be found.

Testing of the Vega device follows Surrey County Council's and NHS Surrey's announcement of  plans for a new app that lets people with illnesses such as bronchitis, diabetes and heart disease do vital health checks at home without the need to visit a surgery or hospital.

Surrey County Council’s Melanie Bussicott, who is in charge of the trial, said: “The county council is always willing to embrace innovation and when we heard about a watch that gives people with dementia more independence in their daily lives, we had to give it a trial.”

Ms Bussicott said: “Our readiness to harness technology to improve care looks to be paying off. “A passionate cyclist is getting the freedom to keep on pedalling while also giving his family the peace of mind that his dementia isn’t going to mean he ends up getting lost.”

The GPS system is implanted in the digital watch. The device contains a battery and a Sim card, which tracks the wearer.

Relatives can log in to a secure website at any time and an alert is triggered when the person goes outside a set radius, with a monitoring centre manned 24 hours a day informing relatives.

Wearers can also press an emergency button, which immediately alerts operators at the centre who send someone to help.

In Surrey’s test, relatives have access to the online map, as well as the monitoring centre.