I kind of wonder how they did this testing. Much of the information we get about a person's mood is from what context there is (far more than comes from what's on their faces). There are people who cry out of joy, but if I saw a picture of one of these people, I'm sure it would look like sadness to me.
Further, I don't like the sound of a future where people stop talking to other people because a light starts blinking.
However, for the purposes of autism research and development, this is good. Better than good - this is excellent. I really hope there will be more research in this area, for the purpose of helping those who can't communicate well. (I suppose that contradicts what I said above. Perhaps there is a particular scale on which to rank necessity of aid in communication?)