An anonymous reader writes with a snippet from Hack a Day: "Clap On! Clap Off! was super awesome when The Clapper came out in the mid-eighties. Now [Mathieu Stephan] is trying to make the concept much more functional. He put together a controller that lets you knock on walls to control things around the house. It's called the Toktoktok project and uses small boxes to receive user input and control items like lamps and computers."
As the project website
points out, Stephan is keeping the project intentionally open.