Kinky jokes aside, this sort of thing can give a pretty good overview of how much you slept and how well. I use a piezoelectric sensor plate from an "Angel Car

Kinky jokes aside, this sort of thing can give a pretty good overview of how much you slept and how well. I use a piezoelectric sensor plate from an "Angel Care" baby monitor. Takes only a handful of passives to safely interface to an Arduino analog pin (safety: The transient from the thing getting jolted not burning out the input pin). The result, graphed (at 1 minute per sample bin - don't get kinky ideas) gives a very good overview of awake/tossing and turning/really asleep. Which to a lousy sleeper like me can actually be reassuring - yes, I did get some sleep in all this.