I've been using the SleepTracker Pro for about two years now and I love it. Just last week I started to have some issues with it - when I would press the light button it would short and everything would be reset. The CEO called me the next day and said that it didn't matter how old the watch was. Send it in and we'll get you a new one. Pretty cool. So I would highly recommend them.
The other part to this is that these types of alarms will only "go off" at the most optimal time. That doesn't necessarily mean that it is any easier to get out of bed. It took me a few months to get used to this fact. You have to get a mentality that when the alarm goes off, you get up. For instance, if I went to bed at 1am, I would set the alarm for 7:15. I would set my "wake window" for about 1.5 hours beforehand. For the first few months, if my alarm went off at 5:45, I would wake up, feel great, look at my clock and realize that I still had over an hour that I could still sleep. So I'd go back to bed and wake up feeling horrible.
Then, I got some great advice from a friend of mine who said, "Sleep like a dog." In other words, sleep when you are tired. Play when you are awake. This broke the mindset I had had since I was a child where I woke up with my alarm to now, as soon as I start to wake up (whether from my SleepTracker or just naturally), I think 'Am I rested? Did I sleep well?' If I had, then I don't even look at the clock, I just get up. Otherwise, I'll stick to my safety alarm clock that always goes off at 7:15.