Cheap and Capable Video Monitoring Server?

An Anonymous Coward asks: "The company I work for is looking to invest in some security/surveillance technology. We are currently using an out-of-the-box, purpose built solution, but for the price it's pretty unreliable and leaves a lot to be desired. The specific need is for cameras to monitor areas of a site, with motion detection, the ability to integrate with other systems via simple boolean conditional switches, and a video web server. Naturally I would prefer to use a PC, as the reliability/price would be much better and the system would be more configurable. Zoneminder looks quite good, it's a Linux based OSS solution, but I'm not sure it's ready for a commercial implementation. Are there any good DIYish solutions around or are expensive consultants and esoteric hardware the only way to go?"