The app, a work-in-progress, will be demoed at Google’s I/O developer event in San Francisco - rare exposure across the Atlantic for a service that so far runs only in western Europe and Scandinavia. The app includes pre-caching of tracks for offline use and, of course, tracks playlisted in the desktop app are mirrored whilst mobile. It’s no surprise that Spotify is unveiling its Google (NSDQ: GOOG) Android app at Google’s own conference, but Android handsets’ poor battery life may hamper its success as a music device. Further mobile announcements are due in the coming weeks and months from Spotify.