Brian Schiffer and Sima Mitra, from Cornell University, propose a very nice wristwatch that allows you to keep track of your time perception, using a method known as duration production: TicTocTrac.
Human perception of time is typically distorted, due to the different amount of information and experiences acquired everyday. TicTocTrac lets you to estimate your own perception, first by signaling the perceived duration of a given event and, then, by comparing it with the actual event duration. Finally, all the information can easily be saved to a micro SD card.
The hardware is based on a Atmega32u4, a DS3234S real-time clock and several leds to display time, while the software part is mostly based on Arduino’s DS3234S RTC library.
More information can be found here.