thanks for the code, this option is realy nice to have!
i think about a way to integrate the free bitcoin mine into drupal https://github.com/Xenland/MiningFarm/ wonder if that sounds interesting? the actual standallone 5.0.1 version looks like this: http://miningfarm.com/
I see the combination of the farm with a BTC based shop like you created it by using drupal quite usefull.


tenobis
http://mine.tenobis.com/