In the meantime there's a wonderful version of John Cage's "4:33" here: http://www.youtube.com/watch?v=yoAbXwr3qkg
But keep quiet about it.
A video that simply showed a timer counting down four minutes and 33 seconds would be even better.
Live performance on every viewing.
Watching a blank video has a similar effect: You start to hear the ambient sounds... traffic outside the window, the ticking clock in the corner, the 60Hz hum of your electronics, the creaking as you rock in your chair, air whooshing through the conditioner vent...