While we don't need an app to tell us that we're stressed out, wouldn't it be interesting to find out how stressed out we are. In a quantifiable manner. The folks over at KDDI thought so too, and came up with an app and hardware combination for Android phones to do the job. While it's not available for sale (it currently is an experiment by KDDI's R&D team), it was recently demonstrated on video.
A user puts on some sort of headband that is used to monitor the user's brain activity, and then he/she is given a simple game to play on the Android device.
Ubergizmo, KDDI mind-reading app tells you how stressed out you are
