I’ve got this down pat – I haven’t been using an alarm clock for about a year. The only thing I’ve missed was a 6:00 wake up for a soccer tournament I didn’t really want to go to because I had a stress fracture in my leg and running hurt.
Reduce the amount of sleep you get into six thirty minute naps, and your body will apparently compensate by quickly dropping in and out of REM sleep. And you will feel as rested as ever once you acclimate yourself, although you sleep only three hours per day.