Braintime
You're playing this game. It's the simplest game in the world. Its almost boring... You just keep doing the same thing. As you play your mind strays, then comes back, then strays again.
Braintime makes you play a game for a set period of time and measures how quick you are over time. At the end it shows you your performance over time. Were you most focused at the beginning and then got lazy at the end? Or did you start slow, peak, then lose interest?
Players can send their play data to a server at the end. The aggregate of this data of many players may show interesting patterns in focus. Perhaps there are classes of people; maybe there are groups of people who lose focus quick, maybe there's a group of people whose focus gradually increases... Maybe it's something else entirely!