At its I/O 2016 show earlier in the week, Google slipped in some news that Play Store apps—with special focus on games—will now have a section in the store called “Google Play Early Access”, which works pretty much exactly the same as Steam’s Early Access.
It’s designed for apps “that are available only as open betas and aren’t in production”, and anyone wanting to take part can opt-in directly from the Play Store, instead of having to go to Google+ page listings like some kind of mobile masochist.
You can see in Google’s image up top how it looks, with the “games in development” section highlighted.