The Anti Sleep Pilot automatically registers the conditions that affect your level of tiredness when you drive. It helps you to stay alert while you drive and constantly calculates your fatigue level using reaction times from tests which maintain alertness, among other things. It uses these personalized calculations to recommend that you take a break when you are about to hit a critical driving fatigue level, and thus prevents accidents.
In addition to monitoring your driving using an accelerometer, the Anti Sleep Pilot will give you a little reaction test every once in a while. It will make a sound and turn orange, at which point you have to smack it as fast as you can. The longer it takes you to do this, the more concerned the device gets about your reaction times, and if you’re too slow on four tests in a row, it will turn an angry red and demand that you pull over and rest.
via: Anti Sleep Pilot