OneNote for iPhone 6

Microsoft has decided to merge both of its OneNote iOS apps. The separate versions of the note-taking apps for the iPhone and iPad have now been replaced by a universal app that works on both products.

iPhone OneNote users won't need to do anything other than get the latest update for their version. However, OneNote users on the iPad will need to download the new universal version from the App Store in order to continue using it. iPad OneNote users will also be able to access features that have already been available by iPhone owners, including the Today widget, the Recent Notes view, and page previews when the iPad is in landscape mode.

Source: Microsoft