Article starts out lame but then gets very good. Worth reading all the way through. In the 1980s some nerds figured out how to use hidden computers to beat roulette, by placing bets after the ball is already spinning and the computer can time its movement to predict (nowhere near perfectly, but well enough to have a statistical edge over the house) where it will land. There is a fantastic book about the adventure, called "The Eudaemonic Pie". The guys in the article managed to do the same thing without computers, and it drove the casino detective nuts.
If you like the article, the book is also great.