3-electrode EEG devices don't really work and that's one of the reasons why biofeedback was a fad of the 1970s. There are some very slick devices out there now like
https://choosemuse.com/
but at that price it is not going to replace the Polar H10 in my biosignals kit, the respiration radar or the GSR and EMG sensors -- and any of those hidden under coat can tell my phone to tell me that I tilted before I realize it on my own.
