Sorry for the shameless bump, but I thought some might find it interesting. I have had this idea in mind for over a year, and as a matter of fact myself and a couple of folks from Stanford have just started implementing it and we would certainly welcome any Python/JS devs who would like to contribute. It's a gevent/websocket-based Python backend with a shiny-like reactive computing engine with planned support for pandas as the primary data format; and an AngularJS-based frontend which allows for some crazy reactive/lazy evaluation not only on server side, but in the browser as well. Graphics-wise, we intend to create wrappers for matplotlib (which is pretty straightforward) along with some cool JS libraries like NVD3, Vega, sigma.js and other. The public repo will be on github in the next few weeks or so, please ping me on twitter @aldanor if interested.