PopApp is a really simple tool, for iPhone and Android, that lets you:
- Draw-out your idea for an app
- Take photos of those drawings, and
- Stitch them together.
The result is a crude prototype and lets you see and feel how your app might look and work.
We use it often (with final screens that our mobile designer has created in Photoshop) in user testing: before we write a single line of code, get a sense of how users might interact with the app, what they might find confusing, etc.