You may also be interested in shortcutd program from the repos, as it allows to assign custom terminal commands (including scripts or whatsnot) to half-press of camera button - both long and short.

This way, your silencing script could be run by pressing camera button in your pocket, instead of taking whole device out to access desktop widget.

Of course, proper way to implement this would be replicating ways of silencing phone signal (maybe you should post a enchancement request at CSSU bugtracker? Your point is absolutely valid), but it would require some coding (and some good coding, too, if one would like to write it right, without taxing battery due to polling - relying on IRQ, instead).

/Estel