Those Crazy Pitch Matching Things

I don't know what they're called, but does anyone know of the effect that corrects pitch? It's used a lot in pop songs on vocals, makes people sound a little like robots. I was wondering if they can be hooked up to a theremin. I know it would take out a lot of the expressiveness of the instrument, but I think it would also make playing easier. Does anyone have any experience with these?

They're called Pitch-Correctors (also rarely 'auto-tuners'), and to be honest I absolutely detest them. They take almost all the skill out of anything involving making your own notes, and they are becoming (unfortunately) better and better at doing their jobs. They still are distinguishable from normal vocal work though, and like you say they often cause singers to sound like robots. There was a period in the late 80s when they first came into heavy use, and they are instantly recognisable. Nowerdays they are much harder to detect though.

If you're playing an instrument like a theremin however, I don't really think that they would be a worthy investment. The fact that you slide between notes would probably confuse the machine and destroy the lucid theremin vibrato. I have heard of people who do use them, but in my opinion you may as well just generate a sine wave and then let the computer play the tune for you.

If you want to be on pitch all the time, and be able to play normall too, then why not buy the new MIDI theremin listed on the front page (name of producer evades me)? That produces both discrete notes, like on a keyboard, and can be set to normal theremin mode.

just learn the instrument

Just thought it might be fun. It would be no replacement for the natural tones The Instrument.

I know what you could do. . . .

. . . . buy a Tannerin! (*boo! Hiss! Boo!*)

What is that^

Oh, sorry. It's like a Theremin, but you play it with a hand-held slider against a picture of a keyboard, a bit like the slide ring of an Ondes Martenot (an early electronic keyboard). They sound almost identical to the theremin, but you can be perfectly on key with them. They were used widely instead of the theremin for film tracks and so-on, because there was no need to re-take so often.

There is a company that still makes them. Do a google image search if you want to see what they look like (for 'tannerin').

"There is a company that still makes them."

Which company might that be? I've been looking for years and haven't found one yet.
If you are refereing to the "Therevox" Electro-theremin, I can tell you right now that that is a cruel joke and the maker obviously has no intention of actually producing electro-theremins for the general public. I "ordered" mine over a year ago and was in contact with the maker often, and I even offered to help him with his design problems. It soon became clear he had no intention of actually following through with the project.