For millions of Americans with chronic medical conditions, careful day-to-day health monitoring can help avert catastrophe. Home health gauges abound, but they take readings only at discrete points in time and require a patient's active participation--answering a computer questionnaire, for example. The ideal monitor, however, would record data constantly, and patients wouldn't even notice it's there. This summer, a few firms take that next step, commercializing wearable health sensors. "There's no question we're going remote, and we're going wireless," says Credit Suisse First Boston's Robert Hopkins.

In March, VivoMetrics of Ventura, CA, began beta-testing its LifeShirt, which looks like a sleek fishing vest and records more than 40 health parameters. Sewn into the vest are electrodes for heart monitoring and three conductive bands that gauge the movement of the heart and lungs from changes in their magnetic fields. The sensors measure both vital signs and indicators of psychological state, like sighing. A belt-mounted device records the data, which can be sent over the Internet to a doctor-who might notice dangerous spikes in heart rate, say, and adjust medications accordingly.