Sleep Cycle Alarm Clock. This is the perfect app to wake you up in the morning and better still, you get woken gently and it's not all jerky so how it works is that it uses the accelerometer to gauge and graph the sleep you get and for how much of it you are awake. Unfortunately i'm not here to tell you how it works. Although I am here to review it so let's get on with it.
Pros: Cheap app at $0.99 (£0.69), monitors sleep and wakes you well, does what it says on the tin, easy to use graphs.
Cons: The phone is to be put next to your pillow so for some people they will not like this app because of it.
Overall this is an amazing app for what it does and the price so CHECK IT OUT!