"Proper" way to Access Java from javascript

I'm working on a Firefox extension that needs to access some native OS
for information.  As an example, lets say I would like to capture the
Output of uname -a and display it in XUL window.

I have accomplished this by adapting with MIT's SIMILE example (http://
simile.mit.edu/wiki/Java_Firefox_Extension).

The small java lib I have written gathers information and returns it
as a JSON formated string.  The javascript in the FF extension calls
this java method and uses the string returned.

>From what I understand (i may be mistaken), the technique used in
SIMILE is somewhat of a hack and I am not sure I want to release an
extension based on this to the masses.

I've read up on javaxpcom, liveconnect, and a bit of xulrunner and at
this point I am confused as to the best way (forward compatible and
blessed by the Mozilla developers) to perform this somewhat simple
task.

So for the functionality I described above, which do you think is the
best method.

And depending on you answers, the specific problems I and having are

javaxpcom: cannot find any examples for js -> java communication

liveconnect:
 - is this true "LiveConnect may be removed from Mozilla 2.0 according
to this post by Josh."
 - for statements like var red = new Packages.HelloWorld();   where do
you place your jar file so it can be found?


thanks in advance,  any pointers/help is very appreciated