Webcams seem like a great idea, and they have been suggested earlier in this thread - but people are doubting their resolution and frame rates. I dont think they'd be a problem, theres some good ones avail these days - not those cheap $20 manual focus ones. I'll might do some research myself for a decent one...
As a starter, Logitech's webcam on their webpage shows 640x480 live video capture, at up to 30 frames per second. Higher resolutions are possible, but for still capture only.
Creative have a web cam with a resolution of 1600 x 1200 pixels, this is equal to 1.9MP which isnt bad!
http://www.creative.com/products/product.a...16425&nav=1