For five months, Google App Inventor, a simplified tool for creating applications for the mobile operating system Android, was available only by invitation. Recently App Inventor has been made available to all Google users for free.
With App Inventor you can create different kinds of android applications. Often people start with the creation of games like MoleMash or similar kind of apps. When developing programs, you can configure the phone sensors to implement motion sensing.
The development of applications in the App Inventor is not limited to simple games: you can even create a program to inform and educate. An example of this kind can serve as a test to prepare for the exam.You can even develop speech synthesis with App Inventor.
App Inventor provides access to GPS so that you can develop apps which uses GPS. It is worth noting that while the App Inventor is in beta stage: Google Labs reports that the tool lacks some features and it has some rough edges. However, this is a great tool for android enthusiasts.
Get started with App Inventor from here.