Noise Maker makes a loud, annoying noise when you shake the phone. This app is meant for sporting events, much like the vuvuzelas that became infamous during the 2010 FIFA World Cup. You can use it to help cheer on your team, or to distract the opposition. The main lesson of this chapter—figuring out when the phone is being shaken—can be useful for many apps. You might wish to use the same shake-detection algorithm for more serious apps, perhaps as a gesture to refresh data.