Essentially the whole "watches you while you sleep [not creepy at all] so it can wake you when you're not in a deep sleep phase." I do use a smartphone for that, as it already has motion sensors, and it is indeed somewhat gentler to wake up to.
(OTOH, if I absolutely positively need to wake up at $TIME, the ticking mechanical bedside clock of my grandfather it is: it hasn't been innovated for a century, needs to be manually wound, is completely independent of any external source, and rings loud enough to rouse the dead)
