Requires G15 Composer (which in turn requires G15 Daemon, see http://www.g15tools.com for more info), pkill and pgrep. Tested and working fine in Ubuntu 11.10
NOTE! At the moment, this plugin assumes that your g15composer, pgrep and pkill binaries can be found in /usr/bin. If not, you'll have to edit the paths in the script file ([nightingale profile directory]/extensions/g15simple[at]geekshadow.com/chrome/content/g15simple.js). All paths are located at the top of that file, for convenience.