Apple CEO Tim Cook speaks Sept. 9 during an event at the Flint Center for the Performing Arts in Cupertino, Calif., where he unveiled the Apple Watch. The device officially goes on sale Monday. Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

The Samsung Galaxy Mega (from left), Samsung Galaxy S4 and Apple iPhone 5 are shown. Apple is expected to announce larger models of its smartphone on Tuesday. Richard Drew/AP hide caption

itoggle caption Richard Drew/AP

One of the earliest iPhone prototypes. This system was pieced together to test early versions of the iPhone's software. Courtesy of Apple hide caption

itoggle caption Courtesy of Apple