As the request for an official changelog has been declined, we could try to create and maintain one ourselves over here on MSO. The changelog would be restricted to fixed bugs and completed feature-requests only (which have corresponding meta posts). Also where possible, verifiable features which have been added but do not have corresponding meta posts (verifiable since they should be confirmable by two independent users) would be included. This could be done by a CW question and answer, if there is sufficient interest and need in maintaining one. I personally believe that there is a need for a change log and would like to see one set up. So, would you like to see an unofficial community change log for the android-app get established? Also, would you be interested in maintaining it?
There's an unofficial changelog for the websites already. So I can see where there would be some sort of effort for this, but I'm hesitant in an alpha app. The application could easily have multiple updates in a day that could fix a simple thing that we'd never know about due to a backend change, or fix something that prevented the app from running. Or heck, even completely killed off at this point (but sounds like the project is in for the long haul).
I'd be all for a change log once the app gets into a beta or release stage. At the moment, we could form a simple Data Explorer query since it updates weekly now. It could look at all the questions tagged android-app with status-completed. Then look at the accepted answer time and/or the answers from a set developer list like balpha and/or Kasra. That would give us a crude change log with a question title, and when it was fixed.