What prototyping tool do you use for iOS apps? There are many tools to prototype apps, but I do use image based prototyping tool for initial stage. So, I can save my time to write codes. I used to use POP. It is a very nice tool to implement simple prototypes w/ idea sketch and lo-fi sketches.
However, I found a nicer app, "app.eal - Prototype your app idea" today. https://itunes.apple.com/app/id608380878
It supports navigation bar and tab bar, and basic transition effects. Moreover, it stores my prototypes on my device only, so I don't need to worry about security issue.
I'm wondering if there is better image based prototyping tools; especially iPhone and iPad apps.