First you will need cameras. Wired are more hassle to install but aren't effected by interference from wireless phones, microwave ovens, wireless broadband, or even computers (as wireless can be). It's a personal choice, I use both. I really like my wired X10 color cam, and I have read great things about X10 wireless WIDE EYE cam.
For totally dark conditions you will need an IR or "night vision" camera. A couple of us on the forum are getting good results with the ASTAK brand. They are inexpensive and easy to find (search security camera at walmart.com). The one I own is wired (not wireless) and I picked it up at a walmart store for $58. Be sure you know the cameras night vision "range" before buying. If 30 feet is your requirement, I would get one with AT LEAST a 30 foot range, 40 foot wouldn't hurt.
To get the camera image to your computer you will need:
Motion sensors like the
EagleEye Motion Sensors (MS14A) to detect the rock thrower (and turn on the camera and notifiy the computer to record).
AHP (Active Home Pro is a USB interface and software).
CLICK HERESomething like the iwatchout software (plug-in) with the
USB Video Capture Adapter (VA11A). CLICK HERE If you want something more like advise, instead of a shopping list: I would recommend you start with an X10 one camera kit that includes the video commander (which will work with a VCR to tape your video). This will get you up and running very quickly, while you build your system. CLICK HERE Of course if your completely new to X10, will will also need a transceiver, and a palmpad remote might be nice too.
I would also increase the outside lighting. I like the motion activated floodlights. Nobody wants to be seen throwing rocks. I would also check the doors, windows and locks all around the house. If you don't have a security alarm, this might be a good time to look at one.