A natural, physical interface to the digital world using a whiteboard.
Do arithmetic and plot equations by simply writing them on the board and the result will be projected in. Think of it like a physical interface for matlab. The result is a real time, reactive system that lets the user change numbers or variables and immediately see the result. A camera on top of the projector does OCR, which is implemented using a neural network and log gradient decent. The US Postal Service's handwritten digit dataset was used to train the model.
This has interesting applications in teaching, since the instructor can present graphs and data instantly and perfectly, saving time and making things clearer. The reactive aspect also make it easier to get an intuitive understanding of the subject because it allows the users to play around with each parameter and immediately see the result.