IP security cameras tend to be expensive,  and have fairly ordinary resolution, no audio, and low frame rates.

But the Aiptek A-HD+ does 1440x1080P @ 30fps and costs < $USD200. 

The question is: Can the A-HD+ plus be hacked to produce continuous video out the USB port and/or, can an ethernet interface be retro-fitted to it? 

This depends on how easy the firmware is to modify, and what sort of hardware the camera is based on. 

I've ordered an Aiptek camera (bought it on ebay for $USD184) and it should be arriving before 2008-Jun-30 so we can find out...