I have recently read an announcement appearing in a very famous Italian Hi-FI newspaper site. It seems that Arduino has been used to control some sections of an Hi-End Audio Power Amplifier !
Look here: http://www.audioreview.it/index.php?option=com_content&view=article&id=1266:le-novita-head&catid=19:nuovi-prodotti&Itemid=60
It is in Italian, but this is the rough translation of the sentence:
"M.U.SI.C.A." is the first High-End Amplifier which integrates HW open Source! Inside the Amplifier, an Arduino Module is in charge to control all the amplifier parts, such as output stage, operating temperature, fan speed...
This confirms once again that there is no limit to the flexibility of Arduino! Great!!!!