Stanley’s level app is available free online at the Apple App Store. It is useful for simple jobs, such as hanging pictures, mounting shelves and more. It harnesses the technology of an accelerometer and a digital gyroscope in select iPhone and iPad models to generate an understanding of where the device is in space. After an initial calibration, the bubble will read an angle up to 90 degrees and will indicate 0 degrees when you are level, with easy-to-read numbers. It is compatible with iPhone 3GS, iPhone 4, iPhone 4S, iPhone 5, iPod touch (3rd generation), iPod touch (4th generation), iPod touch (5th generation) and iPad. It requires iOS 5.0 or newer.