POP is rad. Too often people get stuck making pixel perfect wireframes or mocks when really all you need is a quick and dirty sketch to play with.
A couple of weeks ago we launched the MVP of our iPhone app that uploads sketches into the Marvel web app so you can turn them into prototypes.
Our app can also export sketches to multiple iOS screen sizes.
The next version will have full prototyping capabilities plus some sick features for designers :)
great app. used it myself quite a bit.
@Wraecca POPApp mentioned!
Super app! Love it above invision. Perfect to combo with screen-design in keynote.