Bike theft is a huge problem worldwide but especially in San Francisco with a 70 per cent rise since 2006. That's why police there have started using technology to thwart crime – namely GPS bikes and Twitter. And it's working.

San Francisco police have been using "bait bikes" equipped with GPS trackers to entice and catch criminals. The bikes are left around the city and once stolen they're tracked so the thief can be caught. In a recent example a $1,500 bike was stolen and within half an hour the perpetrator was found and the bike returned.

Officer Matt Friedman, who is in charge of the operation, then tweets to avert further theft. He tweeted, on apprehending the bike thief: "You should have seen his face - he thought he was in the clear." And "Thank You 4 Taking Our Bait Bike." The plan is to scare other would-be thieves into avoiding bike theft.

The San Francisco police department was award $75,000 to fund the scheme which started this year. The University of Wisconsin, who pioneered this scheme, saw a 40 per cent drop in bike theft in the first year of putting it into action.

Apart from Twitter, stickers which say "Is this a bait bike?" are also used to deter theft. Many thefts occur in homes so Officer Friedman recently tweeted: "If anyone is willing to let us camp out in their garage for the evening, contact me at Park Station." Just another proactive effort to deter criminals, because they will never know which bikes are rigged and which are not, which garages have police in and which don't.

It's not clear how this isn't entrapment. Perhaps thieves are not arrested with bait bikes but scared into realising their next theft could be an arrest. Since it seems to work we're all for it.

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