Galvanic Skin Response (GSR) and Electro-dermal testing (EDT)
Medical experiments have shown that the magnitude of the electrical conductance in a person's skin is directly correlated to their emotional state. The short term changes in electrical conductances also correlate with a person's mental response. Skin conductance is known to be correlated with an individual's emotional state. It is often used in psychology for quantifying a person's reaction to different stimulus. It is also often implemented in a traditional lie detectors. The current theory is that a person under arousal generates sweat at the skin that changes the skin's electrical properties.
Waveform capture
When measuring skin conductance, there is the skin conductance level (SCL) and skin conductance response (SCR). SCL is the slow varying skin conductance value, changing over the course of minutes. SCR is the fast varying skin conductance value, changing over the course of seconds. The SCR that rides on top of the SCL reflects a person's mental response to various stimulus. SCR has several statistics that are useful for psychologists. First is latency, which is the amount of time between the stimulus and the rise of the wave. Next is the rise time, how long it takes for the skin conductance to shoot up to it's peak. Amplitude is the height of the SCR. Half recovery time is the amount of time it takes for the wave to fall back to half it's amplitude.
GSR has been used for decades by many practitioners and known by many names such as

Quantum E-meter.
An E-meter is an electronic device, similar in purpose to a Wheatstone Bridge, manufactured by the Church of Scientology. A Wheatstone bridge measures the subject's galvanic skin response. It is used as an aid by Dianetics and Scientology counselors in some forms of auditing or spiritual counselling, the application of the techniques of Dianetics and Scientology to another or to oneself for the express purpose of addressing spiritual issues.
The E-meter measures changes in the electrical resistance of the human body by inducing a tiny electrical current through the body. According to Scientology doctrine, the resistance corresponds to the "mental mass and energy" of the subject's mind, which change when the subject thinks of particular mental images from the past (engrams) whether in this lifetime or others.
The Church of Scientology restrict the use of the E-meter to trained professionals, treating it as "a religious artifact which can only be used by Scientology ministers or ministers-in-training. It does not diagnose or cure anything. It measures the mental state or change of state of a person and thus is of benefit to the auditor in helping the preclear locate areas to be handled.

The use of the E-meter, GSR, EDT is confined to "bona fide religious or spiritual counseling" and is not medically or scientifically capable of improving the health or bodily function of anyone.