Why in the world would you want micro-second accuracy? It would be entirely useless, even from a scientific standpoint.
I don't think there is a display in the world that has mega-hertz refresh rates. The best LCD TV's out there, refresh at 120Hz. Even Plasma's don't refresh more than 600Hz. Your brain wouldn't even be able to interpret numbers moving that quickly.
So, you can make your own micro-second clock. Just use a standard clock, and instead of actually telling time for the digits after a thousandth of a second, just have a slightly morphing blur graphic. The net effect would be the same. If you wanted, you could even "pause it" and display random numbers in place of the blur, the accuracy of which would be arbitrary.
http://www.youtube.com/watch?v=hYETzTT6jbY
not entirely useless