Ive been reading the info about a project with great inspiration! And what about your rivals in blockchain?
As far as I know, there is no other proposal for uniting independent Android App Stores around an open protocol.
There are some projects ICOs related (Dmarket, mobilego) with exchanging digital virtual items inside games and tournaments, but that is outside the scope of AppCoins.
Projects like BAT, have some similar concepts (pay for attention) but is browser based.
Some months ago there was Spherius project for generic software stores (Windows,...) but didn't reach the soft cap.