How does this differ to popapp ( https://popapp.in ) which I've been using for over a year now ?
* Our iPhone app ties in with our web app, which allows you to prototype both web and mobile. http://www.marvelapp.com. Our iPhone app is just one part of the eco-system
* We support PSD importing directly into the iPhone app
* All your images are synced with Dropbox so you can easily access them
* Our web app allows you to download prototypes as ZIPs to run offline or on your own server
* You can select dozens of different device frames (HTC One, Lumia, iPhone 5S etc)
* You can export iPad prototypes using our iPhone app
Sometimes I feel like HN asks "how is this different from X app" without doing any research, just to be lazy.