I have a Withings sleep pad that sits under my mattress and I find it significantly more accurate than other decives I've tried. It also easily tells between a

I have a Withings sleep pad that sits under my mattress and I find it significantly more accurate than other decives I've tried. It also easily tells between activities in bed (even motionless ones like reading or watching) vs sleeping (and all the assorted cycles). It also measures heart rate, breathing (and how many times you stop), and even snoring.