Proponents of the Electronic Product Code (ePC) unique numbering system want to put a tag on every object in the world, writes Sean Nicholls.

Before too long, everything you buy - from the shirt on your back to a can of baked beans - could come embedded with its own tiny electronic tag - a kind of tiny bar code. You won't even know it's there, but guess what? The manufacturer will ...

By transmitting its presence to sensors inside factories, warehouses, shops and your home, an ePC will let manufacturers track every one of their products from the factory to the shelf and finally, in the case of the shirt, to your back.

All you have to do is agree to go along for the ride by installing the sensor that will register the ePC signal in the first place.

That doesn't mollify privacy groups. Worst case scenario: surveillance marketing, whereby companies know exactly where and how you're using every one of their products; put that information together into a consumer profile and it's a marketer's dream.

ePC isn't here yet but it's not all that far off: it's at the heart of a new electronic product tracking technology called Auto-ID. Taking a keen interest in its development are companies that probably produce a significant proportion of the goods you use today: they include Philip Morris, Proctor and Gamble, Gillette, Philips, Unilever, Tesco, NCR, Coca-Cola, Pepsi, Johnson and Johnson, AC Neilsen and Pfizer.

Auto-ID, currently being developed at the Media Lab at Massachusetts Institute of Technology (MIT) in conjunction with those sponsor companies, relies on �smart tags' that use Radio Frequency Identification (RFID), a wireless technology which has been around for a while now. Those security tags you find slipped into novels at book stores are a common example of RFID.

RFID has major advantages over traditional bar coding: it's more durable, it can be read over relatively long distances (up to three metres) and it can store large amounts of data.

A similar breakthrough RFIDbased technology was announced by Hitachi early last year. Called the mu-chip (as in micro chip), it's tiny (0.4 millimetres square) already costs just a few cents to make and is easily incorporated into just about any product you care to name, including paper.

Both technologies herald a new era for product manufacturers and, we're told, should bring related consumer benefits.

By running an ePC past the sensor, you'll be able to call up detailed product information quickly and easily (the sensor connects to the Net for you); products could talk to each other, one understanding how to cook another, for example; product recalls are quick and targeted; you will never have to wait in a shop queue again.

Privacy concerns are brushed aside as unwarranted: the types of tags embedded in everyday objects won't transmit longdistance and, in any case, consumers will have to agree first before products could be tracked into their homes or on the street.

But privacy groups are already asking questions about what happens further on. They say if these devices can already be incorporated into products, who knows how they could be used in future?

Auto-ID began its first field tests in the US in October. The trials will run for nine months.

The company doesn't expect the technology to make an appearance until at least 2003-4. Hitachi says the mu-chip will be ready to go this year.