[DerKommissar]

Reminded me of a great sleep app I used to use. It's called Gentle Alarm and it really is a great hack. I don't know if the authors of the software came up with this idea but it works great.

Here's how it works. If you are woken up when you are deep REM sleep you will feel tired. If you wake up when you are in very light sleep you will not. This is what happens when you wake up naturally. The sleep cycle generally repeats itself every 90 minutes or so but everyone is different. The point is there are times you can wake up when you will feel refreshed, and times when you will feel tired.

Gentle Alarm configures two alarms. It plays a very soft alarm half an hour before your real alarm (all the times and volumes are configurable). If you are in deep sleep at that time you will not wake up to this alarm but if you are in light sleep you will. If you are in deep sleep then in half an hour (or whatever period) you will almost certainly not be in deep sleep. You will then wake up to your normal alarm. The system ensures that you are awake by your alarm time.

It worked amazingly well for me when I needed it.