Wow, that's pretty nifty. Somehow I missed it when I looked at the home page. Did you change it? If not, I think I might have missed it because local was only in the finer print. If the header said "Worry Free Local Fallbacks" I think more visitors will notice it.
BTW please see my other comment about changing the API; "secret" in client-side JavaScript is confusing.
Edit: never mind, didn't realize my other comment was replying to you. You've already noticed that secret is a misnomer. :)
Does that work for CoffeeScript files? Looking at proxino.js, it doesn't appear to work for it. If you could have a version that included the CoffeeScript compiler, I'd be very likely to use this.
After signing up I received an email asking if I had any questions. I asked this one, and they responded that they don't support it yet, but they're working on it.