Today, we’re announcing a Cortana application for Android phones and for iPhones which works as a companion to Cortana on your Windows 10 PC. The ‘Phone Companion’ app on the PC will help you install the Cortana app from the Google Play or Apple App Store onto your phone so you’ll be able to take the intelligence of Cortana with you, wherever you go.
Microsoft first launched Cortana last year in response to Apple's Siri. Immediately following its launch on Windows Phone, rumors began to surface indicating that Microsoft was considering bringing the personal digital assistant to iOS. Microsoft continued to expand Cortana and brought the personal digital assistant to Windows 10, which is launching later this fall.
Cortana for iPhone and Android will contain most of the same functionality and features as its Windows Phone and PC counterpart; however, Microsoft notes that since Cortana will be an app that users download on their iPhone, there will be some limitations. Some features require deeper OS integration and access that is not possible with an application. For instance, to start Cortana, users on Windows Phone and PC can simply say "Hey Cortana," but this will not be possible on iPhone and Android devices.
In addition to Cortana for iPhone and Android, Microsoft also announced a Phone Companion app for Windows 10 PCs that will help setup your mobile phone (iPhone, Windows Phone, or Android) with your Windows machine to help ensure a seamless experience between the two devices.