In a surprise announcement today, Google stated that the Google Clock app for Android will be updated this week to support a new Spotify integration. That integration will allow you to set the Clock app to play music as your alarm instead of the range of tones already available.
The news is surprising for two main reasons. First, Google has had a clock app for years and the decision to put in this somewhat basic feature now is a bit of a mystery. Second, why Spotify? The feature works for both free and premium subscribers to the service but why not use their own Google Play Music? The feature, as it appears, only supports Spotify for the integration.