An example app for Udacity course 'Building Scalable Apps with GAE
Since the course application is build using Cloud Endpoints, you can also easily generate libraries for building mobile applications, and this app showcases a native Android app, that connects to the server developed in this course.
This app connects to Udacity hosted server, but you can download the apk and source code for this app from GitHub, and follow the instructions on how to make it work with your server. The source code for this application can be found here - https://github.com/udacity/conference-central-android-app