This is a fascinating app. It is an app that can monitor your sleep patterns. For 99 cents, it certainly is worth trying. I have used it when stressed, and also when taking a Tylenol PM, and you can really see how those things affect your sleep pattern. You place the app under your pillow, and make sure it stays plugged in so it can monitor and charge throughout the night. You can also set an alarm and the app will determine when you are in your lightest sleep with a 30 minute window to wake you up. It records your sleep graph and saves it for you to refer to.

According to Sleep Cycle:

Sleep Cycle monitors your movement during sleep using the extremely sensitive accelerometer in your iPhone. 
Sleep Cycle then finds the optimal time to wake you up during a 30 minute window that ends at your set alarm time.Look at the screenshots for recommended iPhone placement.As you sleep you go through different phases that range from deep sleep to light sleep. The phase you are in when your alarm clock goes off is a critical factor regarding how tired you will feel when you wake up.Since you move differently in bed during the different phases, Sleep Cycle uses the accelerometer in your iPhone to monitor your movement to determine which sleep phase you are in.Sleep Cycle then wakes you in your lightest sleep phase.Sleep Cycle was developed using proven sleep science and over a year of testing.Sleep Cycle also saves your sleep data and displays a detailed sleep graph and sleep statistics for every night you use it.

This graph shows a normal sleep pattern:


This graph shows a more irregular sleep pattern with a period of being awake or nearly awake at 6 am:


Finally, this graph shows what your sleep pattern would look like under the influence of alcohol:

I would encourage you to purchase this app to see how your sleep patterns vary from night to night.

Have you used this app before or something similar? Leave me a comment and tell me about your experience.