Thanks for your feedback.
I have about 360 nights video-recorded while sleeping with a Fitbit (out of about 1,200 nights video -recorded) and have been looking at how well it can track my sleepwalking. The results are pretty bad for Fitbit (and any other device I have tested).
If considering only times when I got out of bed, Fitbit sees them only 50% of the time.
If I includes all sleepwalking activity (things like sitting in bed and searching the bed) it drops down to around 10%.
I am still looking to find someone that has done a similar correlation, not necessarily in relation to a sleep disorder, to better understand what data from those devices is reliable. At this point I only consider sleep onset (from an aggregate of at least 3 devices) and a changing heart rate to be reliable. But would love to use more than that, should I see some evidence of accuracy, since I have tons of data collected.