Does anybody know of how Band 2 interacts with Android? Like does it sync with the Cortana Android app, notifications, etc.?
I don't quite know what "sync with Cortana Android app" you mean. It does sync emails, calendar events, texts, phone calls, etc. Also allows keyboard responses to texts from the Band (which I believe is still missing from Apple devices).
If you mean does it allow you to open the Cortana app on Android from the Band 2 by long pressing the function key on the Band? Yes, it does that too. In short, I don't think there is anything I used to be able to do with the Band 2 and my Windows phone, that I can't do with the Band 2 and my Android phone.