Video/Audio Security Solution?

IpSo_ asks: "I work for a medium sized company with many locations across Canada. Each of our offices has at least 10 (some up to 50) computers, and are very public places, so they are a quite common target for thieves. (10 computers go "missing" each year on average) We have a Linux server, and high speed Internet in each location. In short we are looking for a cost effective way to install a entire video surveillance system. (remember, this is many different locations, so multiply the cost 15-fold at least) What would be the best way to have several cameras (some with microphones perhaps?) capture video and broadcast it over the Internet? I was thinking something along the lines of those X10 wireless cameras with a video capture card that supports Linux, but it needs to allow for 2-10 cameras. Motion sensing software would be wonderful as well, but not necessary. Any ideas?"