Knock on Wood

Tree-mounted Machines Connect to Web App to Let Users Knock on Wood Remotely

Knock on Wood is an internet-connected device that performs the familiar gesture of knocking on wood, allowing users to follow the superstition remotely when no wood is nearby.

Through a web app, users press a digital button to trigger a physical device that knocks on wood in real time.

Each knocker connects to the internet and communicates with a central server, allowing multiple devices to respond to users around the world at the same time. 

[via designboom]