Flinto, interactive prototype apps for iOS.
The prototype design is important in the development of any app because you can evaluate your idea, the scope of application and also highlight problems or virtues. For these tasks, Flint is a good alternative.
This tool for Mac is excellent for prototyping applications for iOS, the remarkable thing is that it is very simple to use and you can add your prototypes animations, gestures and scroll for text or images, plus you can also connect all screens in your application.
If you use sketch you can use the plugin to import your work Flinto, real-time view your work running on your iOS device and share your prototype because the viewer is free in the App Store so you can send it to your customers so that you see and evaluate.