[kermit_de_fro]

I won't argue with your feelings toward Emotiv, since I don't especially trust their demos to be well controlled for various muscular cues.

That said, there is good work done which puts a lot of effort into actually measuring the non-muscular signal from EEGs and training on that instead. EEGs can capture signal from alpha waves (roughly analogous to alertness as you describe), and researchers have come up with numerous specific responses to watch for. One such example is the P3000 response, corresponding to the reaction a person has when they are shown an object which they were picturing in their head (a target).

There are numerous other techniques, many dealing with predicting a type of pattern by looking for activity coming from the corresponding area of the brain. If the sensors and algorithms are written correctly, EEG can absolutely be a neural interface, although one with quite a lot of noise. Done poorly, it can be entirely swamped by the physical motions you describe.