It's good point! However, one of the main benefits of a technology like this, would be not really for everyday people, but for people with handicap or a speech impediment.

I personally have a stammer. While mine is less severe, and I doesn't need directly it, I know several people that would quite be glad of the benefits that it could bring to them. (Example: pass online interviews).

I agree however of the privacy concerns. We could limit it in a first time to medical devices for example, or have some privacy laws in place.