The Office Mobile for iPhone and Android suites are both like the Office Mobile suite that Microsoft preloads on Windows Phone, meaning they are optimized for the editing, viewing and creation of Word and Excel documents. (Microsoft already has offered OneNote for Android phones since February 2012.) Unlike Office Mobile for iPhone, Office Mobile for Android phones does not include an option to purchase an Office 365 subscription from within the app, however. Office Mobile for Android phones only has a “sign in” option.
Office 365 subscribers are authorized install Office Mobile on up to five iPhones and/or Android phones. (Office Mobile on Windows Phones don't count against that total.) Office 365 University subscribers can install Office Mobile on up to two non-Windows Phones.
One internal Microsoft roadmap I saw indicated that Office for iOS and Android might not arrive until the fall of 2014. But it was unclear from that roadmap if this was a reference to Office for iPhones and Android phones or Office for iPad and Android tablets. If the fall 2014 date was simply a reference to the new Office Mobile suites, Microsoft may have decided to push these cross-platform versions of Office for mobile devices out more quickly than planned not so long ago.