The "sobriety tags" aim at enforcing abstinence by measuring a person's perspiration every half an hour and testing for traces of alcohol. If any trace is discovered, an alert will be sent to the offender's probation officer and they can then be recalled to court, where they could face sanctions such as a fine or even be re-sentenced.
The 12-month scheme is being trialled in four London boroughs - Croydon, Lambeth, Southwark and Sutton and is being backed by the Metropolitan Police and the Mayor of London, Boris Johnson.
The tags register alcohol consumption, but do not keep track of people's movements or where they are.
Up to 150 offenders could be fitted with the tags under the new scheme. They will be banned from drinking alcohol for up to 120 days, and the tag will test them to see if they flout the ban.
Offenders will be screened before they are chosen to wear the ankle tag. People who are alcohol-dependent and need specialist support will not be a part of the scheme.Other reporting indicates that the transdermal ankle tags measure the alcohol content of perspiration.
They are apparently an extension of the Secure Continuous Remote Alcohol Monitoring (SCRAM) bracelet.