iOS Design Kit - The newest library of native iOS templates
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
iOS Design Course - The Complete iOS Design Course with Sketch from Bitfountain
Smartmockups - Create stunning product mockups, easily and online.
Xcode - Xcode is Apple’s powerful integrated development environment for creating great apps for Mac, iPhone, and iPad. Xcode 4 includes the Xcode IDE, instruments, iOS Simulator, and the latest Mac OS X and iOS SDKs.
MockMagic - A free, easy-to-use device mockup generator