In researching this particular app I learned that iHandy is more than just the level app. They also have an iHandy Ruler App, iHandy Protractor App, iHandy Tip Calculator and a whole lot more. I was really impressed with the easy directions for use. They even tell you how to calibrate your iPhone to ensure absolute reliability.
And my favorite iHandy App has to be the iHandy Coin Flip. You pick the coin and with a double tap or a flip or your wrist you test your luck.
For more information, download instructions, or how to use visit: http://www.ihandysoft.com/level/