If Google Play Music and Runtastic are your favorite running companions, this collab was meant for you. The Big G's Play Music division has teamed up with Runtastic to put free workout playlists within the Adidas-owned fitness app itself. All you need to do is fire up its music section to access, say, a collection of 130-beats-per-minute tracks that can match your steps, electronic dance music or high-energy rock tunes. You'll be able to pause, play and skip within Runtastic, so you won't need to switch apps anymore.