Apple has unveiled the iPhone Duo, its first foldable iPhone, with sales set to begin October 23. The new model opens to a 7.6-inch inner screen and carries a 5.4-inch outer display. Apple says the larger panel offers the biggest screen yet on an iPhone. U.S. prices start at $1,999 for 256GB of storage. Preorders begin October 16 across more than 70 countries and regions.