Microsoft was one of the early pioneers of "swipe-to-type," a software later adopted by SwiftKey, Google, and others. Instead of pressing every key, a user can swipe between them and the phone guesses the word based on whether the finger is and where its going.
Microsoft told a small group of Windows Insiders that the keyboard was coming to iOS, but did not give a release date. Microsoft has also bought Cortana, the virtual assistant, to the iPhone.
Business Insider has reached out to Microsoft to ask about Word Flow coming to the iPhone. We will update the post when we hear back.