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.

VivoMetrics anticipates its first customers will be drug companies trying to gather better data in clinical trials. “There’s the possibility we’ll be able to detect subtle changes that are not picked up…in the doctor’s office,” says VivoMetrics vice president for health care Bill Cary. U.S. Food and Drug Administration approval should come this summer, Cary says.

Still, it’s hard to imagine millions of people wearing fishing vests to the office. Addison, TX-based Sensatex believes that its fabric–woven from optical and electrical fibers–will allow the integration of electronic components into more conventional clothing. Sensatex concentrates uniquely on production of the fabric, but it expects that its corporate partners will introduce monitoring products using its technology by next summer.

Nexan of Alpharetta, GA, on the other hand, doesn’t bother with wiring clothes. Its sensor–which looks like an elaborately bent paper clip–adheres to a patient’s chest and radios data to a storage device up to 15 meters away, which can be hooked into the Internet. Electrodes in the sensor measure respiration and contraction of the heart. Nexan hopes its system will aid in the clinical evaluation of patients with congestive heart failure and looks for FDA approval this summer.