Tokyoflash has designed an LED watch.
When you first glance at it, you will probably see a bunch of green waves, but if you look at it closely, you can see past the optical illusion and see the actual time displayed.

If for some reason you've been staring at it for more than five minutes and can't figure it out, you can opt out and hit a button that will remove the illusion and display the time in a more conventional method, which is probably the smart thing to do if you're trying to tell the time while driving.