Well with the old card I don't have a problem, it is lost in the noise and the machine runs 24/7 for other reasons anyway.
If I decide to get into this seriously however I plan to buy a high end card (ATI 6xxxx series) and dedicate (one or more) old/cheap machines to it.
THEN the power costs get significant - particularly with a 20/7 (plus HVAC cost!) ratio.
My present thought is to simply put the whole machine into hibernation or standby mode via a cron job.
Right now I have 3 old machines sitting around that could be put to use under a counter (or something).
I've got a script running on cron that runs every 5 minutes just to check that the miners are indeed working and that my graphics cards aren't exploding. It's quick, simple and it works.
I like your idea of checking to see if things are still alive - hadn't though of that one! Thank you!
Of course all of this depends on the ratio of cost of mining to the value of Bitcoins - right now at US$15/BTC it works nicely, but in 3 weeks - who knows?