This dial widget is an advanced rotation control that you can easily include into any Android project in the form of an AAR file (Androids’ equivalent of a JAR file). You can think of this Dial control as a gesture library that is just concerned with rotation; having all of the conceivable behaviour you could possibly want in a rotation control. It comes with a free demo app.
WinValidaition is a simple, yet powerful rule-based UI validation library based on annotations for Android.
Routable is an in-app native URL router, for Android.