Many people came through the Nottinghack tent looking to borrow tools or materials but these guys really stuck with it and decided to make their whole thing with us. When they asked if I had something pulley like I suggested we laser cut the whole deal. I wish I had a video of the final item but hopefully someone can link me over to it.
They were using an app on an I phone that could calculate the distance to a laser dot. They built this turret which would turn the laser dot and the iphone together and shine about waist height. The Iphone fed data back to a laptop which played a note based upon the distance. It worked really well and was very cool when people gathered around it to see what they were doing creating a tune (or at least a not that irritating noise)