If you have the app open to the paused screen, it is going to be using
some battery even if the emulator engine is not running yet. It
should not be using any significant battery when it goes to the
background. I wish I had a kindle fire to test but I have had a
couple of oddball comments from kindle fire users that I've never
heard about on other platforms. Maybe their software was more alpha
than beta.
I'll look at the battery drain on my GNex tonight if I get a chance.
Thank you for the report.
Garnet