The Economist, March 3, 2012 at 20, describes a nascent movement of people who measure aspects of themselves over time. They describe an investment banker who wears a headband at night that tracks sleep quantity and quality by measuring brainwave activity. The data from that tool, along with other information the banker tracks, such as diet, caffeine and alcohol consumption, and exercise help him sleep more soundly. Other examples suggest that in-house lawyers might learn much about their patterns of alertness and concentration if they measured themselves more. Passive devices of all kinds can (or will) track stress, engagement, break points and more (See my post of Sept. 22, 2010: pomodoros.). For example, the article mentions an adhesive patch that measures heart rate, posture, motion and temperature, all of which bear on intellectual sharpness and duration.
Why not have gauges that gives us clues as to our stamina, logginess, best time of day for thinking? Self-quantifying monitors will be available to guide us to greater productivity (See my post of July 29, 2007: ambient orbs.).