The Russian police have decided to set up equipment which will read the data on mobile telephones of passengers as they are waiting for subway trains.
The head of police for Moscow's subway system, chief Andrei Mokhov, told Izvestia the device would be used to help locate stolen mobile phones.
Mokhov said the devices have a range of about five metres and can read the SIM card. They will then check to see if the card is on a kist of stolen phones, and it is then the system automatically sends information to the coppers.
Then the time and place of the alert can be matched to closed-circuit TV in stations so that the suspect can be filmed to make his arrest much easier.
However. Izvestia quoted experts who said that the devices can be used more widely to follow all passengers without exception.
Mokhov said that it was illegal to track a person without permission from the authorities, but that there was no law against tracking the property of a company, such as a SIM card.