Absolutely Awesome! One more thing is needed, however. The ability to be able to save the modified sources to the server (with appropriate security of course, dev-env only). Also the ability to fetch the server sources from the server, if e.g. I'm running a Node.js and I want to debug and edit the JS in Chrome - along with the client side JS, side by side.

The close we programmers are to the "living code", the better. The file-watching, auto-reloading and re-executing BDD's (or TDD's, etc.) like vows (http://vowsjs.org/) get pretty close to it, but it's not the same.

When I'm coding a function, I want to be able to run it anytime (when the syntax is OK of course), and in the environment of my program.

Great stuff. Also similar in-client code editing efforts, Firefox: https://github.com/Gozala/sky-edit, general: https://github.com/ajaxorg/ace