Blues guitarist
Joe Bonamassa currently uses a Moog theremin on stage.
There's a "gear interview" up on YouTube that has him talking about it and a bunch of other instruments and equipment he uses.
Link here:
http://www.youtube.com/watch?v=D7S9bQNkr7kTheremin discussion starts at the 1:40 mark if you're impatient.
There's an nice vid of him playing Spike Driver Blues on baritone guitar 
where he uses the Theremin to good effect towards the end. (I'm amazed the Metal crowd hasn't jumped on doing this sort of thing yet.)
IMHO this is probably one of the more viable attempts to integrate something like a Theremin into popular music. Joe's use of the "T" is neither gimmicky nor overwhelming. With him, it's just one more available color on his sonic palette. Very cool stuff. 
EDIT: cancel that. Wrong video. The one I wanted has been taken down apparently. This vid is ok but there's not much theremin on it.
Link here:
http://www.youtube.com/watch?v=o9eeRiyjoLw-----
@Edvard - What, you too?
Over the years I put together two or three courtesy of some electronic magazine articles. But I could never get the oscillators stable or good sounding enough to be musically useful.
Bob Moog was a big fan of the theremin. He maintained that the biggest two problems with the Theremin were that (a) people lacked respect for the instrument; and (b) that instrument companies were unwilling to put the time and money into doing one up right. Which is why
he eventually did.
And which isn't much of a stretch when you consider how the theremin is basically a variation of a dual-ribbon controller. And Moog was pretty big on those too if I remember correctly.
- carpe noctem
