Sorry, I was far from clear. I didn't mean to suggest that a proxy
server approach was the way to do this, but mentioned it to show
that CGI is a rational choice for the browser <-> extension interface.
That is, I see it working like this:
browser get's protocol it doesn't understand
it builds up all the CGI environment variables etc. and
forks off some program to deal with it
program does whatever is necessary and communicates back
in the standard CGI ways
No servers and no internet necessary.