I was actually a presenter at one of these before. They used App Inventor http://appinventor.mit.edu/explore/ http://appinventor.mit.edu/explore/ It's actually

I was actually a presenter at one of these before. They used App Inventor http://appinventor.mit.edu/explore/ http://appinventor.mit.edu/explore/ It's actually a good experience for the girls if you plan for it in advance and have at least some knowledge of app-Inventor (I assume they almost always use that).