Get this app on your phone by scanning the QR code below.
If you need a QR code scanner, download ZXing from the Android market on your phone.
Make your own custom version of this app by downloading the source and modifying in App Inventor.
download the zip file but don't unzip.Then in App Inventor choose More Actions | Upload Source
This tutorial is Chapter 4 in the AI book. It provides step-by-step instructions for building this app.
See the refined tutorial here: