[sdiy] lo cost theremin?

[creekree at gmx.de]

hi,

yesterday my girl and i watched this ooold movie and they used a 
theremin for the ufo sound... she liked the sound, i like her - sooo why 
not build a theremin for her?
it seems there are a few different approaches to this, so could anyone 
recommend a simple one that does not require hunting for long obsolete 
parts and similar obstacles? any links and insights welcome :)

thanks, christian