Creating an App Inventor app begins in your browser, where you design how the app will look. Then, like fitting together puzzle pieces, you set your app’s behavior. All the while, through a live connection between your computer and your phone, your app appears on your phone. App Inventor, and the MIT App Inventor service, are provided by MIT at the Center for Mobile Learning. You can build many different types of apps with App Inventor.

http://beta.appinventor.mit.edu