iPod nano (6th generation)

Apple cut the nano down to a 1.54-inch square touchscreen with a clip on the back, no click wheel, no video, no camera, and a 38 percent smaller body. It looked exactly like a watch face, which is what a lot of people immediately did with it. Third-party watch straps for the sixth-generation nano became a real cottage industry, and one of them raised nearly a million dollars on Kickstarter in 2010, which was an enormous sum at the time. Apple noticed. Whether or not this is where the Apple Watch began, the company was watching several thousand people solve a problem it had not thought to address.