I remember seeing that myself, (so your not going crazy), it appeared to be (though i cannot be certain) a copper wire formed into a coil and attached to a current. (the only thing that this coil was attached to was the current supply (ie it was not driving anything itself, it was just the coil hovering 'while' current was supplied).

the guy explained that it was some sort of principle (i cannot remember what principle) but i am guessing that electomagnetics had something to do with it.

y