Another option, which will free up all of the computers in your home, is the Dropcam Wi-Fi security camera.
For about $200 and a $10 monthly fee, all you need is Wi-Fi to monitor your house from anywhere in the world, using your computer or mobile device.
Motions trigger alerts, which are sent to you via text or e-mail. Then you can watch the video from your phone. The interface is dead simple and takes only five minutes to setup.
One drawback to security systems like these is false positives, set off by roaming cats or dogs. But some programs include a thumbnail image of what the camera sees in the alert text or e-mail. That way you can know if the motion sensor was activated by a real intruder or your pet.