How can I watch for uninstalled app updates?

What is the best, non-manual, way of checking to see if an app that I do **not** have installed has an update? For example, I do not have Google Camera installed, but I may want to install it when a new feature I'm looking for has been added to it. Is there a site place such as Google play or Playboard that I can get an rss feed, email or another way of notification for certain apps? EDIT: I am now aware of the defunct app "Changelog Droid" which is no longer maintained since January 2014. "*The app is currently not maintained. There is an (unlikely to be fixed) issue with paid apps. Please don't contact me in this regard.*" So a solution beyond that would be greatly appreciated.