Please learn this term now: epidermal electronics. Researchers at the University of Illinois have created a small electronic skin patch that can replace all those sensors and cords that hospital patients normally have to deal with. The patch is capable of detecting vital signs and transmitting that information.

From the BBC:

The device is small, less than 50 micrometres thick – less than the diameter of a human hair.
The sensor is mounted on to a water-soluble sheet of plastic, so is attached to the body by brushing with water, just like a temporary tattoo.

But unlike other temporary tattoos, it’s actually a semiconductor and can draw power from tiny solar cells. What? I know!

This from Popular Science:

Inventors say they could be used for various medical applications, especially sensors that monitor heart and muscle activity, which currently require conductive gels, tape and wires. To prove it, they measured electrical activity produced by the heart, brain, and skeletal muscles, they report in this week’s issue of the journal Science.
Studying brain function in a normal environment is impossible now — to use an EEG, a patient would have to be in a lab setting or wear some type of complicated helmet — but the patch could make it possible. Or imagine a patient with a degenerative disease who cannot communicate, but could use the patches to connect with a computer.
In a throat patch experiment, the patch was precise enough for the research team to differentiate several words, according to the National Science Foundation. They were even able to control a voice-activated video game with better than 90 percent accuracy.