Here at the office, we pulled a prank on a co-worker (filled his overhead cabinet with packing peanuts), but the person that instigated the prank was leaving the company before the prank could be "revealed". So, I took an old PII laptop, installed WinXP on it (unregistered), then configured my D-Link DCS-1000W web cam (stand-alone wireless camera) to gather the images. I installed the IPview software from the D-Link website to capture the stream, and, since this was all wireless, put a Linksys wireless reouter in between to create an infrastructure 802.11b network.
Well, the camera caught the prank "reveal", but for various reasons we had to move it ot a sub-optimal location, and the "stream of peanuts" was unfortunately obscured...
The IPview software ran over the long 3-day weekend, streaming to the laptop, and on Tuesday AM, it captured the prank, and the instigator fo the prank has been sent the video to enjoy the fruits of his labor.
Similar cameras have motion detection built-in, but this one does not. If I had more time, I could have wired an alarm circuit "trigger" to capture the prank (magnetic reed switch inside the cabinet door).
Being wireless really made the install of the camera simple...