[andai]

How do you wake up when you need to, if the amount of sleep you need varies? I have the opposite approach, by waking up at the same time every day, my body makes me sleepy at the appropriate time (which varies by day). Once I get into a rhythm, I wake up on my own, slightly before the alarm goes off.

[bradstewart]

I had a fitness tracker/wearable (Jawbone I think) that would track your sleep, and vibrate to wake you up at the best point of your sleep cycle within +/- 15 minutes of your set alarm time.

I really like the idea, but the thing would always fall off at night. Maybe I should try a new one...

[wpietri]

Mostly by going to bed earlier and by having a wake-up time that normally gives me plenty of time in the morning. Also by being comfortable with biphasic sleep, where I might be up for 90 minutes in the middle of the night. (That appears to be the natural human sleep cycle; an uninterrupted 8 hours became the standard only once electric light became common.) And occasionally by taking an afternoon nap.

On the rare occasions when I have something pretty early that I absolutely have to be awake for, I'll use a sleep-cycle-sensitive alarm. I use the one in my Pebble, but there are plenty of others.