Editor's Note: This story was originally posted in the January 2004 issue of Scientific American.

Thirteen years ago, in an article for Scientific American, the late Mark Weiser, then my colleague at Xerox PARC, outlined his bold vision of “ubiquitous computing”: small computers would be embedded in everyday objects all around us and, using wireless connections, would respond to our presence, desires and needs without being actively manipulated. This network of mobile and fixed devices would do things for us automatically and so invisibly that we would notice only their effects. Weiser called such systems “calm technology,” because they would make it easier for us to focus on our work and other activities, instead of demanding that we interact with and control them, as the typical PC does today.

In a home equipped with this kind of technology, readers strategically placed in the bedroom, the bathroom door frame, the stairwell and the refrigerator would detect the identifying data in microchip tags sewn into your clothes and embedded in the packaging of foods and send the data to a home computer, which would take action based on that information.

The computer would notice as you got out of bed in the morning and would switch on the coffeemaker. As you entered the bathroom, the shower would come on, adjusted to your favorite temperature. When you started down the stairs, the preloaded toaster would heat up so that your breakfast would be done just the way you like it. When you opened the refrigerator, the appliance would remind you that you were out of milk and that the tub of coleslaw inside had passed its expiration date and should be thrown out.

Today systems based on radio-frequency identification (RFID) technology are helping to move Weiser’s vision closer to reality. These systems consist of tags (small silicon chips that contain identifying data and sometimes other information) and of readers that automatically receive and decode that data.

The responsive RFID home—and conference room, office building and car—are still far away, but RFID technology is already in limited use. The tags, often as small as a grain of rice, now hide in ID cards and wristbands, windshieldmounted toll tags, gasoline quick-purchase tokens, and electronic ear tags for livestock, and they have begun to appear in auto key-chain antitheft devices, toys (Hasbro Star Wars figures) and other products. They have also timed runners in road races, and last year a company in Mexico began a service to implant tags under the skin of children as an antikidnapping measure.

In the near term, RFID tags will probably be found in airline luggage labels (British Airways has conducted extensive trials), and they may eventually be embedded in paper currency to inhibit counterfeiters and enable governments to track the movement of cash. (Hitachi in Japan recently announced that it has developed tags minute enough for this application.) Meanwhile the retail, security, transportation, manufacturing and shipping industries are all testing or starting to implement sophisticated RFID applications.

But the RFID revolution is not without a downside: the technology’s growth raises important social issues, and as RFID systems proliferate, we will be forced to address new problems related to privacy, law and ethics. Controversy has already erupted: in mid-2003 two major retailers—Wal-Mart in the U.S. and the international clothing maker Benetton— canceled large-scale tests of in-store RFID-centered inventory control systems apparently partly as a response to public reactions that raised the specter of wholesale monitoring of citizens through tags embedded in consumer products.