The EMF detector, from Supernatural. Turns out that ghosts and other nasties give off electromagnetic fields, which you can detect with a handy gizmo.

However, I have a specific problem using EMF meters. Due to a medical anomaly (extremely high body electricity), I am unable to get an accurate reading on a standard EMF meter.

Jason Stroming, of the NY Paranormal Society: We mainly uses things like EMF detectors, which detect changes in the electro-magnetic field, still and video cameras, and audio recorders.