Building a Small Theremin

I have to admit, I know nothing about electronics or building a Theremin. I am wondering if anyone has an idea how small or flat a Theremin can be made?

I have a novel idea for a gift, but would like to know if it is even plausable. If anyone is interested in making a tiny one, could you please give me an approx size and price? Thanks!

Please contact me using the contact form on my website:

http://theremin.tfrenkel.com

Sent!