'simply' is not a word to use lightly in that sentence.

I've experimented with brain controllers and certainly at the moment, they leave a lot to be desired. At this stage, I'd rather have an unobtrusive clicker/keyer on one hand, a bluetooth throat mike or do gesture detection through the video than any kind of brain interface.

I do have an idea that maybe you could do something with pressure changes in the ear canal, but I'd have to do some experimentation to see if it's really practical.

Basically you want something unobtrusive that doesn't take significant chunks of your body out of action.