Free Protractor is easy to use. The angle can be set by touching the pointer directly or by entering the angle on a keypad. There is also a lock function to avoid accidental movement of the pointer when taking readings.
Full Specifications
What's new in version 1.0
General
ReleaseSeptember 22, 2012
Date AddedSeptember 22, 2012
Version1.0
Operating Systems
Operating SystemsiOS
Additional RequirementsCompatible with iPod Touch (3rd generation or later, iPhone 3Gs, iPhone 4, iPad. iTunes account required.