As many of you may know, Google has provided us with a nice Dashboard that shows us the current distribution of active Android devices along certain characteristics, such as
You could implement Google Analytics ( https://www.google.com.br/analytics/ ) on your app. There you can find all kinds of statistics, including country specific data.
Here is how to implement Analytics on you Android App: https://developers.google.com/analytics/devguides/collection/android/