Can we build a device which would warn us when we go to hypno state. I think this is possible because it is related to brain waves, and would be cool. Hypnosis is not bad usually, but such a device would help us understand what is going on. We don't see such devices, because authorities would be worried about their potential negative uses.

I heard we go to hypno state about 10 times(?) a day without being aware of it. And probably not all are the same.
For example you may get bored when listening to a lecture, it might be a hypno state, or
you may listen carefully and it may be another hypno state (not sure).