My own research has shown that a single EEG channel with traditional techniques gets you into the ballpark of 60% accuracy (another human rater on all sorts of

My own research has shown that a single EEG channel with traditional techniques gets you into the ballpark of 60% accuracy (another human rater on all sorts of data gets you to ~80% accuracy and state of the art methods around 75% accuracy on a single EEG channel). Movement + heart-rate has much less information, so I'd expect about 40% accuracy overall. My work has been traditionally done with AASM sleep labels which may be a bit more complex that what fitbit uses, so that may bring up their overall accuracy. Additionally I assume that fitbit would use a hidden markov model to predict the sleep stages (which can produce very deceptive results in the context of sleep IMO). I'd say that this would bring their overall accuracy up to around 55% based upon my best guess.