Could be problematic
If you are reading the "I think I'll make a fist" signal instead of the directive "make a fist signal." it sound like they are bypassing the secision part. By bypassing the desicion part of the process I wonder if there could be problems of filtering. for example if your neighbor is making you angry and your body starts heading for a flight or fight response, your brain might send a signal saying "I think I'll make a fist." Somewhere in the decision process your brain might decide that making a fist is not the best way to handel the situation, but if you're only readingthe intention, you might have already made a fist. This is it'n most neutral might result in some twitchy unintentional movements and at its worst, escalate a conflict.
That said, the fact they can read that signal at all is really cool.