For years, the smartphone has followed a familiar formula: a screen that fits in the hand, a camera that keeps getting better and a design that changes only so much. Apple is now opening that formula up. On September 9, the company introduced iPhone Duo, its first foldable iPhone, bringing together a compact 5.4 inch outer display and a 7.6 inch inner display in a design built to transform between phone and larger workspace. The new device is more than a larger screen that fo