Hi, this is Wraecca from the POP team, I saw our new product "POP" on HackerNews so I invite my friends to vote, I guess they don't have HN account so they create new. I feel sorry about that!
However, feel free to give any advice about POP :)
I love paper prototyping, so we make an app called "POP - Prototyping on Paper" that turn paper into interactive prototype. Take a look :) http://popapp.in