Zen Alarm Clock... it sounds like some kind of scam, doesn't it? Some New Age, crystal-based frob that's supposed to make you wake up.
But I bought my first Zen Alarm Clock back in ... oh it had to be '96 or so. I was having a hard time waking up, and no alarm clock worked. I can sleep through a jack hammer, and have, literally. Someone recommended this clock and I tried it out, even though it cost $100, which seemed like a ton for an alarm clock. The difference was staggering. Instead of doing something loud and obnoxious enough to force you to wake up immediately, it uses a long series of increasingly frequent chimes, none of which on their own would wake you.
By the time you become aware that it's going off, you've been gradually waking up for a good 10 minutes or so, which means that you don't feel like you're still asleep, being propelled only by the adrenaline release triggered by a loud noise. Instead you're just "up". If you put the clock on the other side of the room, that final act of getting out of bed and walking over to turn it off is usually sufficient, even if you're sleep deprived, to wake you up thoroughly.
My old clock is now breaking down after about 15 years, and it's time to upgrade to the digital version. I just purchased it today, and hope to get it in the mail in a few days. Can't wait.