While getting started with App inventor, one of the first apps that MIT has you make is the Cat Tap App. You tap a cat, and it meows.
The hardest part so far with App inventor is simply connecting your phone or an emulator. I had a phone connected with USB, but then the Genymotion emulator tried to access the same USB. My advice, choose one or the other and save yourself an hour of troubleshooting.
With that figured out, well the results speak for themselves: