By Louise Price
BBC Radio 5 live
An NHS trust has become the first in the country to try fitting dementia patients with tracking devices.
Relatives and police can use the GPS tracker
The Oxfordshire and Buckinghamshire Mental Health Trust has worked with a technology company to develop an electronic tag for people with the condition.
Sue Fulford-Dobson's partner Ian loves to take an evening stroll. Unfortunately, his vascular dementia means he then forgets where he is.
"He is fascinated by sunsets," said Sue.
"So suddenly at eight o'clock at night he will say: 'There's a lovely sunset; I think I'll just go and see if I can see it better'. And that's when he will disappear.
"I mentioned to our GP this was becoming a problem. We'd had a couple of really bad incidents where we'd had to call the police out and he'd been missing for more than 24 hours, overnight."
Ian is now one of 20 patients from the Thames Valley and Somerset areas taking part in a two-year trial to test a satellite tracking device, which works by using Global Positioning System technology.
The tracker is worn by the patient or fitted to their clothes and allows their movements to be monitored on a map via a secure website.
A carer can also be alerted by a phone call or text if the wearer goes outside a specific area.
Feeling compelled to walk outside is a symptom of dementia, and satellite tracking has been suggested as a way of allowing people to remain independent for longer.
The trial was run by Dr Rupert McShane, a consultant in old age psychiatry at the trust.
He said: "About 30% of people with dementia get lost at some point, and about 25% of them are locked into their houses by worried relatives.
"With the development of GPS technology, we think people with dementia might have more freedom to go out and they might be safer if they do go out, if it's possible to know where they are if they get lost."
But the idea of tracking a patient who might not be capable of understanding how they are being monitored raises questions about who should agree to use the technology.
Sue says it was difficult to persuade Ian to wear the tracker at first.
"I wouldn't say he's happy but provided I put it in his pouch every morning he will leave it there, which is all he has to do.
"I think if somebody is really, really unhappy about it then you can't do it - because people do have human rights.
"As far as Ian is concerned, he is neutral. He says; 'If you think it's of some use I don't mind, but you have to do the work and if you want that, that's up to you'."
In April 2007, the then Science Minister Malcolm Wicks was criticised for suggesting dementia patients could be monitored in this way.
The Alzheimer's Society has since given the technology its backing.
Chief Executive Neil Hunt agrees it could give people more freedom and enable them to walk without the worry of getting lost.
But he says he doesn't want it to become an automatic choice for every patient.
"One size does not fit all; safer walking technology must only be used with a person's full consent and as part of a comprehensive care package.
"It must never be a substitute for good quality care or a way to reduce care costs."
And that's something that concerns others too.
Sabina Frediani is campaigns co-ordinator for Liberty, the human rights organisation.
She said: "A debate about better care for the elderly is a good thing but technical gimmicks often provide cheap and quick fixes rather than dignified and possibly expensive care."
But for Sue Fulford-Dobson, the tracker allows Ian some independence.
"At least it means that if he has vanished, even if I can't find him, it helps the police to find him.
"It would be awful if you had to say him: 'You can't go for a walk, or you can only go for a walk if I go with you'. Because he would hate that."
NHS Innovations, which worked alongside the trust and its commercial partner to develop the device, argues it could potentially save £8m if it reduced the number of people admitted to care homes or hospitals by just 1%.
The commercial developers are now talking to local authorities about supplying them with the technology.
The tracker can already be bought by individuals. It costs £200, and requires people to sign up for a monthly subscription or a pay-as-you-go service.