I've seen on the marketplace now several alarm clock applications that claim to analyze your motion patterns in your sleep, so as to determine the ideal time to wake you up such that you feel refreshed. I am intrigued by this possibility; however, I do not sleep alone. Does anyone know if these apps work well, or even at all, if there are multiple individuals in the bed, each presumably moving on their own sleep cycle?
In short. It doesn't work.
The movements you have when you sleep indicates "muscle paralyzation", which is one of the factors that indicates your REM sleep cycle. However, this is one of the not-so-accurate ones. If you want real accuracy, you will need those that measure ECG with a headband (Zeo, for example).
In addition, most apps in the market does not give an accurate reading of your movements due to interference and sensor sensitivities.