The motion part is easy. It is done totally in software. The program looks at the picture from frame to frame and records when it sees a significant number of pixels change.
I have an old W9x card and the software I got for about $50 that does all this stuff from GranTec. It has 4 RCA ports for composite video inputs from the cameras. I have 2 cabled with RG6 and one RF connected.
The real money is in getting good cameras in the first place if you want "evidence grade" pictures of the bad guys. My cameras are all pretty cheap but I can tell the difference between possums and raccoons when it trips.
