Thanks to duopixel! Found the answer in the thesis pdf. Jump to figure 19. They found a good enough relation between finger muscle relaxation (EMG electrodes) and EEG sleep signals.
This is really cool because you bypass all the other issues/disconfort with other headband devices. I would be much more willing to have something on my fingers during sleep than strapped to my head.
This is really cool because you bypass all the other issues/disconfort with other headband devices. I would be much more willing to have something on my fingers during sleep than strapped to my head.
Edit:typo