That was the inspiration for the Pendulum Clock.You might not see it at first, but it is showing an analog clock face that reads 2:40. Usually it takes a couple swings to see the picture. Once you see it, it becomes very easy to read the time.
The Pendulum Clock has a row of 64 white LEDs that change based on the position of the pendulum. I've used it to display an analog clock face, but it can be used to display any 2D image. The motion of the clock is not powered; you have to manually push the pendulum to one side to start it moving.
It's powered by a simple Arduino Uno, a DS1307 RTC for keeping time, a MAX7219 LED controller, and a bad ass rotary encoder. The case is a Hammond box, which fit all of the components with just the right amount of room. The face is a 4″x24″ piece of basswood.