I still depend on my alarm clock though. I've had this one for about ten years now. I initially started using it because the beep is insanely fucking loud, and I needed that to wake me up because I've slept through fire alarms before. However, now, it's fairly quiet - I think it's wearing out. I'm still a heavy sleeper, but it still wakes me up. I think that since I've used this alarm for half my life, my brain has adapted a tendency to listen for it while asleep and pay more attention to it - the way you learn to wake up to someone calling your name.
Part of me is worried I've jinxed my waking up talent now that I've explained it, but then the logical part of me says "shut up - typing some words on a screen isnt going to change your body's biology." and that's the part I usually listen to.