It seems like it is using Google Cloud Endpoints which means that you can generate client libraries for various languages (Dart, Ruby, Objective-C, Python, JavaScript, …) from your backend API definitions.
See http://www.youtube.com/watch?v=uy0tP6_kWJ4
We are currently looking into Google Cloud Endpoints for exactly this functionality at Blossom (https://www.blossom.io)