Practitioners monitor these signals by means of audio or visual feedback. Technological advances have allowed developers to consider using biofeedback for an entirely new application which is to use these biosignals to control an external device such as a computer. As such, these signals have the potential to be an excellent source of control for assistive devices. For example, the use of EEG to control things by merely thinking about them is now considered a realistic possibility.
Eyes can move a computer cursor, and muscles can make music.
The old dog, Biofeedback, is indeed learning new tricks. Using what amounts to a sophisticated volt meter connected to a pair of electrodes in good contact with the skin, a reliable output can be obtained. The output is directly proportional to the degree of tension in the muscle fibers beneath the electrodes. That is, the more muscle tension, the stronger the signal. Since a performer must be unencumbered, the device had to be small enough to be worn comfortably.