The passage of time can be measured with increasing accuracy, but our own perception of it often diverges wildly from the generally accepted reality. A pair of students from Cornell University, however, are hoping to make clock-watchers more aware of when they believe time is running fast or slow. The TicTocTrac wristwatch, built as an engineering project, is a handsome analog-faced watch with a 3D-printed case and microSD card slot. You can check the time by double-tapping its face, activating LED indicators.
Once the watch is "awake," double-tapping it again will start a time estimation exercise. The screen lights up briefly, showing a random amount of time (between 5 and 55 minutes) for you to wait. Once you think that amount of time has elapsed, you can wake up the watch, which will tell you whether you've overestimated or underestimated. It also logs the disparity on the microSD card, creating a record of when you think time is dragging or flying. According to the TicTocTrac team, this creates a basic form of "duration production," one of several methods used to track time perception. The watch also records when you check it, so you can see when you're waiting for a talk to end or anxiously anticipating an event.
The watch is basically a proof of concept, and the team hasn't expressed any desire to make more of them. What they have done is release full instructions for building your own. You'll need a fairly strong grasp of electrical engineering, but all the relevant details can be found in the extensive documentation, and the team has posted some data taken by testers on the TicTocTrac site.