The Protractor application is a handy tool to measure an angle over the iPhone's camera image.
When you're cutting the cake equally into pieces in front of your friends and children, this application is for you.
1) iPhone with builtin camera
2) iPhone OS 3.1.2 or later
Launching the Protractor application, the camera appears.
The slider is available to adjust the highlighted angles.
The upper-right number shows the value of angles in degrees.
To quit the application, press the 'HOME' button on the iPhone.