I've followed Nick Johnson's tutorial on [Authenticating against App Engine from Android](http://blog.notdot.net/2010/05/Authenticating-against-App-Engine-from-an-Android-app)

Is there anyway to get the same workflow (no web signin) with Federated Login (even if support is limited to Google Accounts)? 

[Edit] *Additional Info*

The current setup includes: 

* App Engine's `UserService` configured for federated login (openId..gmail, aol, myspace?,...)
* Facebook (OAuth)
* Twitter (OAuth)

All the authentication types are wrapped in a `UserService`, so I can call `UserService.getCurrentUser()` (Similar to Appengine's UserService, but supports twitter, and facebook). 

Accounts can have multiple authentication methods linked together.

So far the clients are all web based, and things are working nicely. **:D**

I'd like to:

1. Add a public Api (for web and native mobile apps),
2. use the Api internally for native mobile apps.

What are the options?

I was thinking of limiting authentication to Google Accounts for the Android App, in hopes of avoiding the web based sign in screen. Even so it would be nice to support facebook and twitter for the web Api.