Built with off-the-shelf components, the prototype NAVI device is a black box about half the size of a loaf of bread. The reader includes the CD player plus an antenna that looks somewhat like a singer's microphone. A final version would probably be about as small as a portable CD player. If solid- state memory were incorporated, the entire device could be no larger than a deck of cards. "To prepare a building or site for use with this system will be relatively inex- pensive," says Jack Mottley, a University of Rochester associate professor of electrical and computer engineering. "The tags are inexpensive now and the prices are still dropping. The plan is to use only passive tags that do not require batteries or need to be plugged in, meaning once they are installed they can be ignored." Tags could even be painted over without losing their capabilities. Down the road, NAVI may find additional uses. The technology could, for example, be built into mobile phones or wristwatches. This would allow users to gain information on almost anything around them, from customer reviews about a shirt they're considering buying to automatically paying for a soda at a vending machine. 3.12 WIRELESS UNDERWEAR In an effort designed to protect the health of chronically-ill people, personal garments-even underwear-could someday be equipped with wireless technology. Scientists at Philips Research in Aachen, Germany, have developed a wear- able, wireless monitoring system that can alert patients with underlying health problems to a potentially serious situation, assist clinicians in the diagnosis and WIRELESS UNDERWEAR monitoring of "at-risk" patients, and automatically contact emergency services in the event of an acute medical event. Based on dry-electrode technology that can be built into common clothing items, including bras, briefs, or waist belts, Philips' wireless technology continuously monitors the wearer's body signals, such as heart activity, to detect abnormal health conditions. The technology could pave the way to the deve