Microsoft Band 2 pairs up just fine with Android phones. But if you want to be able to issue voice commands through the wearable, check out the latest update for Microsoft Health. The app's newest version comes with Cortana integration for Android users -- something that only used to be available for people whose Bands are connected to a Windows Phone device.
After updating your Health app, you'll be able bark voice commands on the Band's mic without having to touch your phone and get instant notifications. According to The Digital Lifestyle, though, you have to be in the US (due to the app's limited availability) and have Cortana for Android installed on your phone to be able to use the feature. You can read the application's change log on Google Play, which also lists the ability to create challenges for everyone in your friends' circle who has the wearable.