Journal: Synchronizing Multiple Video Streams Across Multiple Monitors

I work at a production company that creates media and media installations for large corporations. A common refrain amongst our customers is the desire to play synchronous video across multiple computers/monitors to achieve that "integrated" look in a trade show booth or corporate lobby. We've gone down this road before using lumbering proprietary solutions such as WATCHOUT but they all involve a lot of specialty hardware and an unnecessarily tedious setup.

Is there an open-source or super-easy proprietary solution out there that can do this using a simple protocol like midi or an ethernet-based I/O that can trigger basic playback events simultaneously?

The basic ability to slave a bunch of playback machines to a single master control machine is a must-have.