EMF Detectors measure the electromagnetic fields of an area.  It is said that anything from 2-7 milligauss could be spiritual activity.  The K-II is nice in most situations because of the LED lights.  The LED lights allow us to watch for spikes without using our flashlights to look at digital number readings.  

Electomagnetic fields are measured because it is believed that EMF’s may be used to manifest into spiritual activity.  It also helps us locate potential harmful amounts of EMF’s in homes and businesses.  High electromagnetic fields could lead to hallucinations, headaches, and can potentially be very harmful to your health.