Richard Martin has taken a Hama slide viewer, a small screen and a Raspberry Pi, together with some power and audio circuitry, and created this brilliant Aliens-style movie prop. It allows you to sweep back and forth with a corresponding movement of the display (thanks to a compass sensor) and gives out readings of movement with the dread-inducing sound effect from the film. You can see it in action below and see his code on Github. It was based on this tutorial from Virtual Frontiers.