An open source library that lets you easily check your application against your user interface's specification guides. Once added to your app, Peek is activated by tapping the volume buttons. You can then tap on any UI component to see its layout information. Double-tapping presents the Peek Inspectors where you can find a staggering amount of contextual information about the view you're inspecting, including view, layer, layout and view controller attributes, along with application, screen and device level information.