I guess I don't understand the mechanism where by you use an android phone as an external webcam. Guess I never tried just plugging it in via usb and seeing if my OS picked it up...
The OP is literally a blog post on Camo, software that does this.
There are quite a few apps that let you easily do that. I use DroidCam which let's you do it over your local network as well, reducing the cables running to your PC.