Video Viewer displays live video output of system connected web cameras. The application shows all video content in a non-resizeable window (small, medium or large), full-screen mode or embedded on the desktop itself. Video Viewer can be used for monitoring purposes.
Considering its functionality, I compared Video Viewer with Photo Booth. Video Viewer includes a thorough set of preferences for both audio and video output; users can adjust image saturation, sharpness, select a compression type and source (built-in iSight, DV Video, IIDC FireWire Video). Photo Booth on the other hand has none but is more than just a viewer: you can add live video effects and record video input. The only other thing they have in common is the ability to take snapshots. While testing the application with an iSight camera, I noticed that Video Viewer is more demanding in terms of system resources.
Overall, Video Viewer may appeal to those very few using an old operating system (Mac OS X 10.2 and 10.3) as most should still stick with their built-in Photo Booth (OS X 10.4 onwards).