My dad developed a product called "Flag-O-Matic" in the 1950's. It was a portable traffic light controller for construction sites. He built a working prototype, but it was never produced commercially. I'm planning to open it up and check for potential problems, then have it operating at MakerFaire : NC 2011.
The timing circuits in the Flag-O-Matic are all electromechanical -- mechanical timers and relays. What could be built today with an Arduino and a shield board required much more complex circuitry.
More updates as I progress.