Microsoft's Cortana digital assistant on Android can now replace "Google Now" service. The Google Now shortcut (holding the home button) will activate Cortana instead of Google Now. The current version still doesn't include "Hey Cortana" support, largely because of hardware limitations in Android phones that prevent Cortana from always listening for the command.
Download beta version of Cortana for Android from Microsoft by completing the signup process or find the .APK online. 
