Mathias Wandel built the simple, wooden air engine pictured in the video above. It uses a square piston connected to a fly wheel, and has a wooden plate that acts as the valves. If you're interested, he has a page called Air Engine 2 where he describes, with numerous pictures, how he constructed it as well as plans for it you can buy.
He also links to a couple of other folks who also built wooden air engines. One of the fellows -- Donald Zorn -- has a wooden combination lock that he also built, which lead me back around to Mathias' wooden combination lock, which is shown in the video below.