As someone who is terrible at getting enough sleep, I really like the thinking behind this - it's an alarm that's more concerned with when you go to sleep than when you wake up (though obviously that does come into it too; you can enter what time you need to be awake by so you won't just sleep all day). I especially like the push notification you get in the evening prompting you to set what time you want to wake up, so you have plenty of notice when you need to be asleep by.
Pivot