From your own laptop to the power lines outside your home, invisible electromagnetic fluctuations can occur all around us. Use your handy EMF detection unit to spot electromagnetic field oscillations and spikes in the 50-1000 Hz ELF range and the 1kHz to 20 kHz VLF range.
Curiously, this tool is also often used by some paranormal researchers to detect unexplained magnetic fields which they believe to be associated with the possible presence of ghosts or spirits.
Requires 9V battery, included.