It is worth looking at Bruce Schneier' view of this: http://www.schneier.com/blog/archives/2009/04/us_power_grid_h.html The point being that there are no control/SCADA systems on the grid which are also connected to the internet.

If you really want sound on your keyboard, try KeyClick. Sophisticated one for Mac OS X at http://www.sustworks.com/site/prod_keyclick_overview.html (not tried this; it is very old) Windows at http://www.personalmicrocosms.com/Pages/keyclick.aspx