What is that instrument, that somebody keeps putting their hand infront of, detecting? Sometimes it goes up when the hand goes near, and sometimes it doesn't.

What is that instrument, that somebody keeps putting their hand infront of, detecting? Sometimes it goes up when the hand goes near, and sometimes it doesn't. Very cool project. I think if somebody made an installation / toy that did extreme looking ferrofluid stuff in response to people touching around it (like those glass spheres with electricity arcs tracing all around), it'd have commercial value.