TicTocTrac via MakerBot:

Thoughts like, “Time flies when you’re having fun,” or “Lecture lasts forever,” originate from our highly variable sense of time. You have experienced this if you have ever checked your watch to discover that much more (or less) time has progressed than you expected. TicTocTrac is a wristwatch that doesn’t just keep time, but measures your perception of it, allowing you to track changes over the course of days or even months.

Awesome documentation, BOM and schematic included!