Electrodermal Testing is used for the diagnosing purposes by naturopathic doctors.
Are they really safe and helpful?

The first electrodermal diagnostic device was invented in 1958 by Reinhold Voll, a German medical doctor and acupuncturist. He combined acupuncture theory with measurement of galvanic skin responses in the Dermatron. He thought he had discovered that skin conductance was greater at traditional acupuncture points, and he thought he could show that these measurements correlated to diseases in the associated organs. He found that the measurements were affected by allergic reactions. He observed that readings changed when a patient had a bottle of medicine in his pocket. He concluded that some kind of electromagnetic energy was emitted from the medicine and that changes in skin conductance predicted the effects of ingesting the medicine.
One of his students simplified the diagnostic system and created the Vegatest.

The testing procedure was originally known as electroacupuncture according to Voll (EAV), but is now called by many other names including electrodermal screening (EDS), electrodermal testing (EDT), bioelectric functions diagnosis (BFD), bio resonance therapy (BRT), bio-energy regulatory technique (BER), biocybernetic medicine (BM), computerized electrodermal screening (CEDS), computerized electrodermal stress analysis (CEDSA), limbic stress analysis (LSA), meridian energy analysis (MEA), point testing, and many more.

http://www.sciencebasedmedicine.org/index.php/13926/