Dameon
WKR
I drink a lot of water before I hit the sack along with a couple of Motrin PM. I typically wake up an hour before sunrise. I usually have to race back to the tent to turn off my iPhone alarm.
My Garmin GPS has an alarm that has worked best for me but I've used my phone and watch too. Phone has battery issues and watch I have slept through (very heavy sleeper).
Garmin. Doesn't kill batteries and if always got it.
It's also not obnoxiously loud