Timing Is Everything, Isn't It? The next time you wave a key card to unlock the door to your office building, think of Charles Walton. Walton's patents on radio frequency identification, or RFID, spawned those electronic door keys. Now the technology Walton — one of Silicon Valley's unsung inventors — pioneered in the 1970s and 1980s is poised to change the way billions of products are tracked.

Prodded by Wal-Mart and the Pentagon, manufacturers will soon be tagging everything from diapers to combat boots with RFID chips. The chips transmit information about products' location and use over radio waves to a central computer. Libraries are using RFID to keep tabs on books while hospitals embed radio chips on pharmaceutical bottles to make sure drugs are not misused. A Barcelona nightclub scans RFID chips implanted under patrons' skins when they want to pay for a drink wirelessly.

For Walton, industry's embrace of RFID is bittersweet. Back in the 1970s, the bar code was a 25-cent solution that beat out Walton's $1.75 RFID cards as the identification system for goods scanned over supermarket checkout scanners. Now RFID may well eliminate the ubiquitous bar code.

Walton, 83, made about $3 million from patenting RFID technology. But his last royalty-bearing RFID patent expired in the mid-1990s, meaning that he won't share in the potentially gigantic windfall that will be generated as Wal-Mart and the Defense Department begin to require their largest suppliers to put RFID tags on millions of warehoused goods.