Shutdown handler

Would be nice to have one or two functions, that is/are called before standby (manual/empty batt) and gets a few seconds to run.
I don't like the long, loud vibration, for me it could be much shorter. Baybe it also would be nice to blind an led, show a custumised shutdown screen, deinit hardware on or send a power off message to something
Together with Save data to ram it may also be nice to save some data from ram to flash before going to sleep.