I don't know if there is a way for the person next to the person wearing a glass to tell whether the glass is on or off, but if there is no way then there has t

I don't know if there is a way for the person next to the person wearing a glass to tell whether the glass is on or off, but if there is no way then there has to be one which will take care of the security issues like recording a video, taking a picture etc while talking to a person and that person don't know about the same.