Robotic Connect Four lets you play remotely
When a player makes a move by dropping a disc into a slot, this is recorded by an IR proximity sensor on the first board. The data is then transmitted via an Ethernet shield to a web server.
The second board uses a stepper motor to position discs above the correct slot, and drops them using a servo motor. This process is repeated until the game is done, allowing two players to play the game at a distance.