Incorporating the sensors into a headband makes it possible to monitor some electrical activity in the brain, too. "For a one-time doctor visit with ECG and EEG, it probably doesn't matter whether you [use sticky-sensors] or not. But for long-term use, that definitely makes a difference," says Maysam Ghovanloo, a bioengineer at the Georgia Institute of Technology.

The UCSD group is collaborating with a group at Oregon State University to create a completely wireless version of its sensor, with a Bluetooth transmitter that can relay information to a receiver. "I think what they're doing is a really important contribution," says Eric Topol, director of the Scripps Translational Science Institute in San Diego and a specialist in wireless health. "I think it's very viable and attractive, and it's a welcome addition to the wireless sensor tool kit."

Long-term, Chi and Cauwenberghs hope that the sensors could also be helpful for advancing brain-computer interface applications. "We wanted to build a very sensitive sensor that can acquire signals reliably through hair without any messy gels or abrasion or any preparation. Something that's easy to use and very quick," Chi says. Such sensors could be used to help spinal-injury patients communicate, or even be combined with gaming systems.

But while the EEG sensors can pick up certain brain activity, the sensors must be made more sensitive, as neural activity in the brain is remarkably faint. "Noncontact electrodes are going to be an advantage no matter where you put them on the body," says Rahul Sarpeshkar, a bioelectronics engineer at MIT. "But all of these systems, when applied in medicine, have to deal with motion and the strength of a signal, which makes the EEG more technically challenging."

Cardiac applications may be closer at hand: Chi and Cauwenberghs have data showing that their sensors can pick up signals that are nearly as accurate as those collected using gel-based electrodes. Chi is creating a startup company, Cognionics, to develop the sensors further, and has already begun talks with medical-device companies.