Google seems to have now made it easy for apps to offer in-game rewards for watching ads. You can now watch an ad and win coins. Google has come up with a tool in order to help developers make more money from apps even from nonpaying users.
As of now the feature is said to be in the beta testing mode and will debut in video format. When it comes to developers, the rewarded products can be added to any app using the Google Play Billing Library.
For this no software development kit integration is required and Google claims that it has made it easier to implement than similar competing products.