Smartphone-Controlled Ball Launcher

Andrew and his brother built this great ping-pong ball launcher out of salvaged and repurposed parts. I especially like the 13-ball hopper made from two paper towel tubes taped together, and the clever K’Nex-controlled release mechanism. The launcher is controlled with an Arduino connected to a computer and activated via a remote desktop app from a phone or iPod Touch. See this video for an explanation on how it works.