Do you know any books, articles, examples, screencasts that document how to develop an home screen widget on Android?

I just found these links: 

* [widget design guidelines](http://developer.android.com/guide/practices/ui_guidelines/widget_design.html)
* [Introducing home screen widgets and
the AppWidget framework](http://android-developers.blogspot.com/2009/04/introducing-home-screen-widgets-and.html)

I would like to develop a tiny home screen ticker and I'm searching for the proper way to code it.