Scientific 90 Min Sleep Cycle:- (please read The Science section at the bottom)

Our app has a scientific base. Humans have 90 min sleep cycles. So this app analyzes your sleep cycle and only starts/rings when your sleep cycle is about to end. Off-course the app tries to wake you up within the given alarm range. This way you can get most out of your sleep.
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It is not just any other alarm application.
Scientific 90 Min Sleep Cycle is just the app you need when you go to sleep.
User can chose from range of 30 to 90 minutes(the default is 90 mins). It is an alarm clock app that calculates 90 min sleep cycles from the moment you sleep.Then it does the calculations and wakes you up towards the end of the 90 min sleep cycle within the given alarm range of the user.

Finally, when the alarm goes off,you will get a Fresh Morning..!!
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THE SCIENCE (Our App use this exact scientific approach)
Even if you’ve enjoyed a full night’s sleep, getting out of bed can be difficult if your alarm goes off when you’re in the middle of deep sleep (Stage N3). If you want to make mornings less painful—or if you know you only have a limited time for sleep—try setting a wake-up time that’s a multiple of 90 minutes, the length of the average sleep cycle. For example, if you go to bed at 10 p.m., set your alarm for 5:30 (a total of 7 ½ hours of sleep) instead of 6:00 or 6:30. You may feel more refreshed at 5:30 than with another 30 to 60 minutes of sleep because you’re getting up at the end of a sleep cycle when your body and brain are already close to wakefulness.

reference:
http://www.helpguide.org/life/sleeping.htm#cycle