We have recently been working on integrating Greenfoot with the PicoBoard, an external circuit board that provides a number of sensors:
Using the board allows Greenfoot scenarios to be developed that make use of these extra sensors. Some examples are below. If you want to get started and build your own scenario based on the PicoBoard, download the template scenario which has everything set up for you ready to go.
This scenario doesn't implement any functionality but provides a basis for you to create your own scenarios using the PicoBoard. All the required libraries are in place ready to go.
This scenario provides a playground for exploring and testing the different sensors available on the PicoBoard.
An implementation of breakout controlled using the PicoBoard. Use the button to release the ball and the slider to control the paddle.
An electronic drum kit. To use this, connect one side of all the resistive inputs together and hold them (connected by a piece of wire or similar) in one hand. Connect each of the others to a separate conductive surface (eg. squares of tin foil.) You can then play the drums by tapping each of the different pieces of foil. (The button also plays a sound!)