Digital Cameras As Web Cams?

A not-so Anonymous Coward asks: "I've got a spiffy Canon Digital Elph camera, and have been wondering if I can control it from my PC - that, is can I trigger it to take a picture remotely via the USB interface? If so, it seems a logical next step to turn it into a very (very) nice Web cam for stills at a fairly low frame rate. 1600x1200x24 bit. Also, I'd love to try my hand at digital astro-photography (put it on a telescope that is). Seems to me there ought to be some way for me to control it thru the USB again. Anyone with good leads/info on how to hack a Canon digital camera? Seems a worthy hack to me." Some cameras have command line utilities that can be used in scripts to do this. I know Kodak-compatible cameras can do this via ks or the DIGITA ^[?] scripting language, however I'm not so sure about Canon's Elph series. This also might not be too hard a capability to hack into gPhoto.