London is trying out a new way to keep alcohol-fueled crimes down: blood-monitoring technology. People convicted of committing serious crimes while drunk will be given an electronic tag that's able to measure their blood alcohol level. If an offender drinks again, the tag calls the cops. “Offenders will have to ask themselves if a drink is really worth a night in jail,” says Kit Malhouse, London's Deputy Mayor for Crime and Policing. One in five violent incidents in the UK happens at or near bars and clubs, and nearly half of all violent crimes there last year—almost one million—were committed under the influence. Now London cops are hoping their program will show positive results like the South Dakota sobriety project that inspired it: the 24/7 Sobriety project—which mandated twice-daily Breathalyzer tests for convicted drunk drivers—kept 99.3% of offenders sober, causing the prison population to fall by 14%. A Greater London Authority survey shows that Londoners strongly support the new program.