Power Saving Utilities for PBs???

I am curious if anyone knows of any good power saving utilities for my 12 inch PB? I am specificially looking for a utility that will automatically adjust the brightness of the screen and other settings depending on whether the PB is connected to a power source or not. I find it a pain to manually turn down the brightness each time I unhook my laptop. Also, I would like to change the processor speed when I am disconnected. Thanks in advance.