Most mobile robots do this using a technique called SLAM (simultaneous localisation and mapping), whereby they build up a map of their unknown environment, using various sensors, whilst keeping track of their current position at the same time.

BBC: NEWS | Technology | 'Guessing' robots find their way

The technique is based on the fact that mobile-phone companies keep information about the telephone numbers called, and where calls are made and received, for billing purposes.

ECONOMIST: Forensics

Rotenberg sees the ZBVs as mobile versions of the same full-body scanning technique that has tested Americans' tolerance for intrusion as it's been deployed in airports around the country.

FORBES: Magazine Article

This technique shows Scandinavian societies to be very mobile.

ECONOMIST: Measuring social mobility

In a paper soon to be published in the Journal of Applied Physics, he describes how he and his student, Eric Wu, are employing the technique to help with the design of receivers for mobile telephones.

ECONOMIST: MONITOR

All of that means, Hulton and Muller argue, that their cheaper technique is simply drawing needed attention to a problem that mobile carriers have long ignored--one that well-financed eavesdroppers may have been exploiting for years.

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The new technique may serve as a wake-up call for mobile carriers, which have long been in denial about the vulnerabilities of GSM security, says Bruce Schneier, encryption guru and chief technology officer of BT Counterpane.

FORBES: Wiretapping Made Easy

The camp's re-engineering awards went to a group that developed a technique to alter the ID numbers on Global System for Mobile Communications cell phones and to another team that found a way to defeat a biometric fingerprint scanning system.

CNN: Reporter's notebook: Hackers on holiday