AFAICS, right now we need to refresh web interface in order to get new data. But now there are WebSockets that (if I understood them well) can make an almost real-time interface without the need of refreshing the whole page over and over.

It would take quite a lot of work and refactoring, maybe a possible long-term goal. But the improvement would be huge in my opinion.

I'm not sure about this, I've never used WebSockets myself, but I've seen a monitoring tool (also with a web based application/interface) using them in a Symfony2 conference and it's awesome.
I guess you should use this:
https://pypi.python.org/pypi/websockets
in sensor.py and/or server.py.

Then also change the web application to make use of those WebSockets. This comes to my mind:
http://plugins.jquery.com/Websocket/
since I see you're using jQuery in the frontend.