Say hello to RFID: radio-frequency identification. If you don't know about it already, you're going to. Because, depending on who you ask, RFID technology is either a giant can of WD-40 on the wheels of commerce and inventory, or a spawn of the evil military-industrial complex that (still) plans to enslave us all.

The truth is——all together now——somewhere in between.

RFID technology involves "tags" and "readers." An RFID tag can be as small as a postage stamp or a grain of rice, and it's placed on or in something——a pallet being shipped, a box on the UPS truck, or a consumer good like a razor or a can of soup. (Tags are cheap: less than 25 cents for some, and that price is going to drop.)

An RFID reader might be in the entrance to a warehouse, in a handheld computer, or at a cashier's station. When an RFID tag gets in range of a reader, it sends the reader information about itself——whatever's programmed into its memory. "Pallet 5819155 from Flushing," or "Gillette Mach 3 razor from batch 16449905" or what have you. The tags don't need batteries; they get their power from the signal sent by the readers.

Think of RFID tags as high-tech bar codes, but with two very important differences. First, bar codes need to be held a few inches from a scanner, and need to be visible——picture a supermarket cashier swiping a loaf a bread over his scanner. But RFID tags only need to come within about 10 to 30 feet of a reader, and don't have to be pointing a certain way. Walking past an RFID reader with something carrying a tag is enough.

The other difference is the amount of information. Every can of Campbell's chicken noodle soup has the same bar code——it says "This is a can of Campbell's chicken noodle soup." But RFID tags can store up to two kilobytes of information. That's about 2,000 characters——including spaces that can be more than 300 words. It's enough to say (to a computer), "This is can number 2003173451 of Campbell's chicken noodle soup, produced at 3:48 PM on August 8, 2003 at the third processing station in the Newton, Iowa plant. It was canned by a machine operated by Steve Smith because Jeff Jones was out sick that day." (That example, by the way, is about a quarter of a kilobyte.)

So that's RFID: miniscule transmitters that can be placed (or hidden) on any product you can imagine. And they're already in use all over: as security devices in car keys, in warehouses to track inventory, in the ExxonMobil SpeedPass quick-payment keys, and in automatic toll-paying systems like New York City's EZ Pass.

That's nice, you say——I like my car being secure and I like to zip through toll booths. Retailers and shippers like RFID, too. It makes it easy to track goods as they move through the warehouse, or make sure library books don't walk out the door, or keep track of inventory on store shelves.

And thus we bump into the other side of RFID technology——the side that can track your movements once you're carrying something that's tagged.

This could be a good thing. You might approach Schick's smart shelf with a Gillette razor in your cart and trigger a coupon for a free trial. And that's cute when only a few things have RFID tags in them. But it's only a matter of time before most things sport the tags. And while Gillette puts its tags in the packaging instead of the razors themselves (so once you get home and unwrap it, it's gone), other companies might not be so accommodating. Would you know if there was an RFID tag in your lipstick?

You are what you buy. At least, every time you walk by an RFID reader. Let me toss out some scenarios: You go for a job interview, and your prospective employer creates an inventory of your personal possessions. Or maybe your prescriptions. And you thought Google searches were sneaky. The state puts an RFID chip in your driver's license and readers along the highways.

RFID technology is here, and it's in use all over. The first smart shelves are being deployed, and the tags are showing up in more and more products. So if your local police hand out complementary pocket-sized flashlights, stop and think.

Andrew Kantor, CyberSpeak: Tiny transmitters give retailers, privacy advocates goosebumps. December 19, 2003 USA Today.