Medium and high-risk psychiatric patients at the South London and Maudsley NHS Foundation Trust are being tagged with satellite tracking devices.
Under a pilot scheme, the trust has fitted more than 60 patients with ankle bracelets containing a global positioning system technology as a condition of their day leave or while they are being transferred between hospitals.
The GPS device, known as a Buddi tracker, was originally designed for carers to track dementia patients who wandered from their homes.
Last year, The Oxfordshire and Buckinghamshire Mental Health Partnership NHS Trust became the first in the country to use a similar tag to help people with dementia, which can make people forget where they are.
The ankle bracelet in use in South London costs the NHS around £600 per patient. It contains a mobile phone chip and GPS locator and enables a patient’s movements to be tracked to within a few metres anywhere in the world.
If a patient wearing the device leaves a specific area or breaks their curfew, police can automatically be sent an alert. This can contain the patient’s estimated location to within 50 metres, along with personal details and a picture.
Since February 2008, there have been 15 incidents where patients have absconded from the trust. One man was eventually found in Canada.
A spokeswoman for the trust said: "We have a duty to provide high quality patient care while at the same time promoting public safety.
"Our medium secure services provide hospital treatment for people with severe mental health problems – many of whom have restrictions placed upon them by the courts.
"We are currently exploring the use of a tracking system to help us provide safe, secure and effective services. Before introducing this pilot scheme we consulted widely with patients, their representatives and mental health charities."
The system was introduced in South London after rapist Terrence O’Keefe, 39, escaped custody at King’s College Hospital in March 2008 and later strangled David Kemp, 73, in Norfolk.