How to synchronize QuickTime video playback with 3 different Macs? Do you know a method to play three (QuickTime) videos in sync on three different machines? At least I would trigger the space bar to start them in sync.
I don't know how well synchronized it would be, but you could try using at (or launchd or cron) to run an osascript command at a specified time.

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.atrun.plist
at 16:12 &lt;&lt;&lt; 'osascript -e "tell app \"QuickTime Player\" to play document 1"'