Motion

Motion is an alternative solution for video monitoring and surveillance. It detects/it works with cameras and it can detect motion (when picture is changed). Is has a command line option. The output files are JPG (for images), .ppm format and MPEG (for video). It supports multiple video devices, take snapshots on desired intervals, execute other programs at different events like motion detection, saved picture etc.
 
This software will monitor cameras and if detects changes in image (when something it moves) will start capture.