Both presentation api and sysapps device capabilities api (Android port) are using broadcast way to send system event notification from native side. Actually, as you said, this can be improved to make it more efficient, the native system event only is sent to the interested instance, not all instances. 

But this PR is just to refactor and simplify the interfaces exposed for Android extension system, not try to improvement the event watching approach.

Seems it is better to do that improvement in another PR, @cmarcelo, do you agree? and let's focus on the extension interface refactoring for Android in this PR.