RFID tags are miniscule microchips, now smaller than a grain of sand. They listen for a radio query and respond by transmitting their unique ID code. Integrated with local wireless networks or the Global Positioning Satellite (GPS) system, they can locate any tagged item - or tagged person – in real time with precision.

A study released in early June by New York-based Datamonitor.com indicates the scale of the invasion. Worldwide sales of RFIDs could triple over the next five years, exceeding $US6 billion in 2010, according to the study. It says over 40 per cent of that market will be in North America, with a third in Europe and a quarter in Asia. The present cost of RFID tags - 25 US cents each – imposes some limits on their use. But a cost of 5 US cents - or less - is on the way. At that price, according to Datamonitor, the tags could become as common as barcode.

Customization enables diverse usage. Many applications upset privacy advocates, and there is an intense effort in many countries to impose limits on RFID technology.

Curbs are being debated in legislatures around the United States, and the Grocery Manufacturers of America (GMA) association is leading the charge against anti-RFID measures. GMA lobbyists argue for the technology on the strength of its ergonomic credentials, saying the tags make the supply chain more effective and efficient. RFID eliminates manual counting and recounting of products in distribution, according to the lobbyists, and helps eliminate theft and problems detecting out-of-stock and counterfeit merchandise. GMA also sees a time when checkouts could be replaced with RFID systems that scan each cart and automatically bill the transaction according to the consumer’s payment preference, without the retail clerk or customer unloading the trolley.

Many other sectors are using or flirting with RFID technology. Elevator manufacturer Otis uses tags to monitor the maintenance status of its elevators and employee work schedules. Delivery network DHL International GmbH is attaching tags to some of the packages it ships on an experimental basis. Major retail chains such as Wal-Mart in the United States, Tesco in Britain and Metro in Germany have introduced it, and Wal-Mart expects its suppliers to implement do the same. Some car rental agencies and trucking companies use RFID systems to track their vehicles and drivers. And at least one airline – British Airways -- plans to implement the technology to help cut luggage losses.

Privacy advocates have assailed RFID technology since it was introduced. Descriptions such as "spy tags" and "Big Brother in small packages" are common. The clamor against the technology from labor is more recent, and dates from the practice of using RFID systems to track employees.

The most recent assault is from Britain’s CMB Union, which warned in a June press release of a revolt against RFID tagging. Representing some 600,000 workers in most occupations, GMA demanded an end "to the dehumanizing of work via the use of new computer and satellite technology, particularly in the wholesale distribution industry that has the effect of electronically tagging the workforce." The union complains that the tags are also being used to monitor breaks and even trips to the toilet, and have introduced the concept of prison surveillance into the workplace.

"The use of this technology needs to be redesigned to be an aide to the worker rather than making the worker its slave," said Paul Kenny, GMB Acting General Secretary, in the press release.

Even the most vociferous opponents of RFID technology acknowledge its compelling efficiency, but they see the human cost as too high.

Sources: DataMonitor.com; CMB Union; Grocery Manufacturers of America