For obese children, the patch could shed light on metabolic problems. Luprano says that the device is intended to be used for remote biochemical monitoring not only for research, but also to fill in the gaps between visits to the doctor.

Often referred to as smart clothes, such health-monitoring systems have been discussed for many years. Chu says that to be a commercial success, the system would have to be easy to put on, collect meaningful data, and convey the data in a useful way.

Currently, the wearable device is wired to a computer that the physician monitors. Eventually, the researchers will have to incorporate a display for the user as well, or take advantage of digital displays that he might already have, such as a cell phone. If the device detects heightening stress levels, it could send the user a text message, for example, telling him to relax.

Rehmi Post, a recent MIT Media Lab graduate who now develops electronic textiles for the companies Adozu and Asteism, is skeptical. "There's so much that can go wrong," he says, because chemical properties vary widely in a person and can depend on mood. "There are all sorts of factors [that are] difficult to control," he says. "A lot of these initiatives are announced and don't seem to make it to the market, because they tend to be expensive." But Post says that he is glad that smart clothes are being studied for health-care applications and that the field is branching out from its roots in the military.