You can now use Cortana on an Android phone. Like, officially. But it's US-only for now and in beta form.
Microsoft confirmed earlier this year that its smart assistant, Cortana, would soon arrive for Android. Cortana is native to the Windows 10 platform. Microsoft said it would still offer plenty to Android users though, such as notifications for sports, flights, weather, etc. A beta version of the Android app leaked out last month. It was then expected to actually launch alongside the release of Windows 10, but it didn't.
Now, however, Microsoft is making things official. It has released a beta version of Cortana for Android. Anyone with an Android phone can download and install the app now, as long as you agree to join Microsoft's testing program. Keep in mind beta versions of apps may be unstable or have a few bugs. If that doesn't bother you, go here to join the beta and grab the new app. Simples.
Cortana is able to replace Google Now, so when you press the Android home button on a phone, you'll be greeted by Microsoft's personal digital assistant instead of Google's. Unfortunately, the always-listening "Hey Cortana" voice feature is not available, but the app does have many other cool features from the Windows version, including a notebook to control the info about you.
Cortana for Android is now available in the US (only) from the Google Play Store. Microsoft said it is planning to roll out the beta to more markets shortly. We've contacted the company to find out if the UK is on that list.