Someone please correct me if I am wrong, but IIRC, they allow the phone to wake up for an alarm when the phone is switched off. So pretty much what we are used to from Nokia (and Jolla) phones, but last time I checked, it wasn't a standard thing to have in Android land (things might have changed, though).
Additionally, SailfishOS (Mer) has quite a nice dbus interface with which you can set any command to be run and have the phone wake up from the switched off state to do it.