Thanks, and great question! My inspiration was essentially to scratch my own itch. Most prototyping tools I've used required too much attention when I just wanted to focus on my ideas. Many are also difficult to share; I've worked with a lot of remote developers in the past and showing them how to use my newest prototyping tool that week wasn't fun.

In terms of where it fits, I'd say anywhere. I use it now when I would normally reach for a pen. Layouts, flows, notes, I even use it to explain implementation details in development. My enthusiasm might be a bit bias though :)

As for how I think it will evolve, I'm still working on that. Every time I think I know where it's headed, someone finds a new use for it. So far I've seen math lessons, blueprints, meeting rooms, etc., etc.