Portable level app
Stanley’s Level app for the iPhone and iPad provides a portable level in the palm of your hand. Upon first use, the app asks you to calibrate your phone. Once completed, the digital level is available anytime and looks just like a real level with an indicator bubble. The farther from 0°, the farther from straight you become. Choose from the classic Stanley cherry wood level or the modern yellow FatMax Level. Available for free at the Apple App Store. Requires iOS 5.0 or later.