I have higher frequency hearing partial loss and can't hear the beep alarm on wrist watches, no matter how loud unless I have it right next to the ear (and this includes the loudest one I know of, the Brunton ADC Pro). I bring along a 1 ounce watch for my alarm clock, the The Invisible Clock-II ( http://www.invisibleclock.com/ ). I set it to vibrate 6 times at high level, and put it in my titanium mug and man, does it wake me up!
I get up at 5:45 normally on the trail. You can use this to beep instead. Here is the vibration options:
"Adjustable vibration intensity, beep volume, number of beeps - if you want the vibration soft and quiet you can set to low. If you want it strong, you can set to medium or high - same for the beeps. And you can set from 1 to 6 beeps."
One AAA battery will last the whole thru-hike. "1 AAA battery (included) - average battery life = 10 to 12 months. Settings saved while changing battery. "
ps. the second loudest beeping watch I know of, is the Casio Referee Watch. Not as loud as the Brunton ADC Pro though. But louder than any other watch I've used. Still, for me, the only thing that is guaranteed to wake me up is the Invisible Clock II and it is only 1 oz.