I thought about Scala, but the Scala plugin for Android Studio is rumored to be buggy and Scala doesn't integrate well with Gradle build system. At least I couldn't get it to work and I gave up after a while. If they (Google) wanted Scala to be supported on Android, they would make sure it isn't such a pain. And some documentation - all I could turn to for help is a handful of random blog entries etc.
https://github.com/jberkel/android-app.g8