Google App Engine is great for those of you in search of a complete, scalable and affordable hosting solution. Especially if you start a project and you don't yet know exactly how successful it'll be (which mostly you never know), how much potential users you'll have and so on, then App Engine is great.
|Figure: Demo application architecture of Google IO session|
So far one had to create the connection between client-side applications, whether from Android or GWT by hand (I know what I'm talking about). This means also to handle authentication issues and so on. The video below - presented at Google IO 2011 - demonstrates the creation of a task management app with an AppEngine back-end (using the Google Datastore as persistence medium) and an Android as well as a GWT app as the client-side front-end. It nicely demonstrates a new template which an updated version of the Google Plugin creates with build-in authentication and Android to AppEngine RPC call mechanism.