I just wanted to say hello and invite you to come check out our webtool for mobile app prototyping. Its html5, fast, user friendly and very intuitive. It enables you to quickly mockup an app, test & interact with it on your phone, & share with clients/team.
You will find a ton of widgets in the Android, Android 4.0, Android Tablet and Win8 libraries that will be useful when prototyping android apps. Or simply upload your own images & screenshots to interact with them and test your UI on your phone. We also have an android app for download to view your prototypes full screen.
You can try it free at www.fluidui.com/editor & I would love to hear your views and opinions. (chrome and safari atm, firefox next week sorry!)