In a post on the Android Developers Blog, Jeff Sharkey demonstrated the use of the new homescreen widget support that is now part of the Android 1.5 software developer kit. These new widgets can provide live data snippets on the home screen and link in to full featured apps, if desired.
Examples of possible widgets include new mail notifications, music player controls, weather updates, or possible the IM status of a friend. They can be developed to update themselves on a schedule set by the developer, or they can be made to rely on Android’s new automatic updating facility.
Sharkey goes on to provide sample code for developing a widget to display Wiktionary’s “Word of the Day”. If you are a budding Android developer, this might be a good place to start.