Jupiter is a powersaving applet, which can switch between maximum power, high power and save power. Definitely it does more than just setting the CPU speed, as the recommendations of powertop change at least when in High Power mode or Save Power mode. The main page of Jupiter claims that kernel settings are tweaked for powersaving. Does anybody know which tweaks are applied by Jupiter?
I just grokked the code from sourceforge. It boils down to:
Not really rocket science but one may derive the one or the other hint for improving any default power manager that only switches the governors.