If you want to turn your sketch or image into an interactive prototype of an iPhone or Android app you cannot go wrong with POP by Marvel.
Turn a paper sketch into a clickable prototype with POP by marvel
It allows you to sketch your interface on a piece of paper, take a picture with their software and add clickable areas that link to different pages. For the test user, the interface will feel like a sketch version of your app mimicking what would happen if you click links and buttons on the page.
