There have been a few signs that Apple has been working on an iPhone stylus. First an apparent slip by Tim Cook about using an Apple Pencil with an iPhone, and second three different patents filed for a smaller stylus and other Pencil technology. Today, the publication The Investor claims Apple is indeed designing a "digital pen" for release as early as 2019.
"Sources say Apple engineers have recently been working on a new iPhone that comes with a digital pen.
“Apple is preparing to launch the phone as early as 2019,” an industry source told The Investor on condition of anonymity. “It is also in talks with a couple of stylus makers for a partnership.”
If true, the Apple Pencil will be one of the few features launched for the iPad, first then the iPhone.
The report also notes that Apple plans to "drastically upgrade" its A-series chip to improve handwriting recognition. In one of the above mentioned patents, Apple detailed how the Apple Pencil could detect tip wear and alert a user to protect from damaging their display.
Apple first introduced the Apple Pencil for the 12.9-inch iPad Pro in 2015.