In 2002, Jonathan Ive (Senior VP, Apple) began working on a preliminary version of the iPad (035 prototype) together with his team. In 2010, the late Steve Jobs reported that iPhone began with the help of an unreleased iPod that had no home button and uses a rubber band for scrolling. The grainy pictures you see in this article are the official images of that prototype.
Additional photos show that the 035 mockup is much thicker and much heavier compared to the iPad2 today. At least we now know that Apple was the forerunner in this kind of technology. But introducing a home button has really helped to enhance the design.