I was watching the Bill Bailey Part Troll DVD, and was wondering what that thing is on the left that he has on the (our) left that he waves and it works as a kind of synthesizer. I Really don't know what it is, and would like to. For those of you who don't know what I'm talking about here is a youtube link

http://au.youtube.com/watch?v=TqDl491ORqM

It's the thing on the left that he waves his hand near and it 'squeaks'.

I first thought there was strings or something in the loop at the front he was playing, but that seemed to be wrong, as it makes noise as he just waves his hand over the device.

Any Ideas?

(P.S I put it under technology because it was more of a technological thing to me, wanting to know what that piece of hardware is. I wouldn't really call it an instrument. If admin thinks it should go into the music/entertainment forum I would gladly delete this topic and re-post it in there.)