Virtual Theremins
The Theremin is a musical instrument that uses the positions of the performers hands to create sound. The Virtual Theremin aims to mimic the Theremin using just a computer and a cheap web camera. It tracks the hands of a performer, using image processing techniques, around a picture of a Theremin superimposed on the video stream. The positions of the hands are then converted to sound that mimics the response of the Theremin.
Peripheral MIDI Controller (pmidic) is a software program that intends to act as a MIDI controller by using various peripheral devices. The initial release(s) will be focused on using a webcam as a MIDI controller with 3 dimensions (XYZ).
The InterOscitor MIDI video theremin
The InterOscitorTM, combined with your computer and a PC/web camera, is a complete musical instrument that you play with your body and hands through the air, with no physical contact. You can play it from 100 feet away, from a few inches away, or anywhere in between.
Webcam Theremin in Hipno Plug-in Collection
Like other video theremins, just connect a standard webcam to your PC or Mac, load the plugin, and you’re up and running. The VTheremin appears to offer 2 oscillators that can be controlled independently by tracking 2 objects in color video.
More info on Theremins at Theremin World.