It is said: “There are 10 types of people in this world, those who understand binary and those who don’t”. If you choose understanding side, then you might want to wear binary wristwatch.
Building such watch is fairly simple and easy, because you only need few components and even simpler code. Elias watch is based on PIC microcontroller which comes in SSOP-20 package. With few difficulties on soldering it to small PCB he had it running. Watch is powered from coin cell battery CR2032. With smart software solution combined with sleep modes this watch can last long. But the main point of wearing this watch to be identified as nerd. I’m not suggesting to replicate this one, but build your own version.