Last year I started teaching an entrepreneurship class at NYU Poly; while it has an official name we affectionally call it “Entrepreneurship for Hackers.” My co-teacher and I essentially teach tools similar to Steve Blank or the Lean Startup to engineering students over 13 weeks.
In our class on prototyping we cover a bunch of tools from crude sketches on paper to high fidelity mockups done in CSS. This is how POP, Prototyping on Paper, came to my attention. It is a brilliant way to do mobile mockups using only an iPhone; simply draw the app, take a picture, and then add links to sew your screens together and make a sample workflow.
One of our teams used this and I was really impressed with how simple yet powerful their prototype was. If you’ve got a great idea for an app this is a simple way to show it to your friends with only an hours work.