Recent reports said that Google was "disappointed" with the adoption rate of Google Music, which shouldn't really be a surprise given that iTunes is a difficult leader to topple, and more importantly, all-you-can-eat subscription services like Spotify and Sony's Music Unlimited are gaining more and more traction in the market. Still, there is some talk that a proper API for Google Music could help adoption. Google hasn't shown any indication that it is working on said API, so "hacker" Simon Weber decided to take it on himself.
Weber has almost completed his API, which apparently is only missing support for non-MP3 music files. Unfortunately, because Weber has been working in Python, the API is only compatible with desktops right now, but since most of the major work is just about done, it may not be too difficult to port the protocol to mobile. Especially if there is more community involvement in helping Weber with his work. If anyone out there wants to help out, Weber has been posting his code at GitHub.