The fast-moving world of crime can sometimes be like a game of cat and mouse, and often the hardest part is working out who exactly are the cats and who are the mice.

It is generally only a matter of time before the villains, put on the back foot by the latest piece of crime detection equipment, manage to up the ante and get hold of the equipment themselves, thus setting the forces of good into a search for something even better. And, of course, vice versa.

Last year a gang in Xi'an, Shaanxi province used its technical expertise to hook up pinhole cameras to about 50 automatic bank tellers and copy the details of 10,000 bank cards.

Police became aware early on that some kind of heist was afoot, but it took them months of scouring through real-time video to break the case, and by that time a lot of money had flown out of many accounts.

The forces of law and order are now wrestling with solving one of the problems that this case highlights: it is well and good to have ubiquitous surveillance equipment watching our movements 24 hours a day, but how on earth can all of it be monitored by human beings?

"The problem many banks face is that they have a multitude of cameras recording what's happening in various places, but they have few human eyes to watch the video to determine whether anything untoward is going on," says Zhao Yong, chief technology officer of DeepGlint Technology, a Beijing company that employs 80 people.

Zhao, who formerly worked on the Google Glass project, says a camera system his company markets can analyze the nature of human movement and send out an alert if, for example, someone has fallen or there is some kind of commotion. Some banks in China are now using it to complement their security systems, he says.

One of DeepGlint Technology's client banks has about 30,000 monitoring cameras in one district of Beijing alone, he says, but the bank has only six employees to watch about 30 screens that carry real-time video from these cameras. Intelligent cameras obviate the need for human monitors, who are prone to quickly become tired and ineffective, he says.

"Obviously a bank can't hire 30,000 security guards, but our intelligent camera system is the next best thing to do that."

The system sends a warning message as soon as it detects any suspicious behavior or breaches of violations by banks' employees, Zhao says.