Metronome
This simple metronome allows musicians to mark time by giving a regular tick sound at a ed rate.
Drag the arm horizontally to start the arm. Tap to stop. Drag the arm vertically to change the tempo. Tap the "i" button to access application preferences.
Do not put your iPhone to sleep by pressing the sleep/wake button. If the iPhone is locked or goes to sleep, the Metronome won't be able to keep time.
This application was provided as sample code for iPhone developers. Somebody far more talented than me made this application and I take absolutely no credit for it. I just think it's cool enough that it should be distributed for free.
The code license states that developers may "modify and redistribute the Apple Software, with or without modifications, in source and/or binary forms". I'm distributing it unmodified for the world to enjoy.