@clintflint - That's one of the reasons I think being able to record sub-vocalization is going to be fairly dangerous. Not because I think people shouldn't use insight into themselves. That could be pretty interesting.
But because it seems like just a short step away from having genuine thought police. What if you were half thinking about killing your boss or something? You would never actually do it, or even think seriously about it, but your unconscious doesn't necessarily know that. And if you subvocalized the thought at work you could be in major trouble.
And that's not even going into how the government might use an application like this. Imagine being able to put this kind of technology on potential suspects. Now imagine that potential suspect is you and you watch a lot of thrillers. Is it out of the question that you might sub-vocalize something you don't mean to, which makes you look guilty?
I think the whole idea is a scary one.