Surveillancesaver

SurveillanceSaver is an OS X screensaver by Michael Zoellner that shows live images/video of over 400 network surveillance cameras worldwide. It's currently in its alpha state but pretty awesome as it is.. Zoellner also has some other projects listed on his site, f.ex. a "mixed reality chainsaw" ? Could be worth checking out.

SurveillanceSaver for OS X:

http://i.document.m05.de/?page_id=438

A Windows version has recently been ported, too:

http://i.document.m05.de/?p=459