The Sonotize app was created to reward people who stream music on Spotify Premium. For every five seconds of a song streamed, Sonotize gives out one point. Collect enough points and you'll be able to redeem them for gift cards at places like Amazon and Sephora. According to screenshots from the app a $5 reward card for Amazon requires 36,000 points, or 120 hours of streaming on the Sonotize app.
Unless you plan on leaving Spotify on all night it doesn't seem like there's a way to reap a huge reward from Sonotize. That doesn't seem to be the point, though. The Sonotize app is more of a passive rewards program, like loyalty points acquired at the grocery store. Sonotize is out now for iOS.