I have a DIY video security system at the house. It uses a Linux box with two video capture cards connected to two security cameras. The Linux box runs an app called motion [motion, motionrpm] that will capture images and videos when motion is detected in a video frame. It works extremely well, except that I need to leave the Linux box running 24/7. It uses between 60-70 watts according to the Kill-A-Watt, so it's a prime candidate for lowering the power bill.
The motion wiki pointed me to a box called the Aviosys IP Video 9100A . It takes up to four composite video inputs, and serves up either snapshots or a real-time video stream over the network. Basically, it's a little Linux box that runs in under 5W. Sold!
Here's the before and after shot, with both boxes plugged into a WiFi bridge.
The motion software supports IP cameras natively, so I set up the software on my main Linux server, pointed it at the 9100A, and just like that, no more extra 65W Linux box running 24/7.
Even better, the guys at Yoics have developed an alternate firmware that allows direct access to JPGs for each video device. It also provides a very nice iPhone-optimized view of the cameras. Their firmware is highly recommended.