Parker Dillmann @ macrofab.com has designed a wrist LED binary clock based on PIC16F527 Microchip mcu.
The Macro Watch stemmed from those constraints. I picked the PIC16F527 microcontroller by Microchip to be the core of the watch because it was the cheapest MCU I could find that had enough I/O and I knew at least a little bit about it in terms of writing code for and programming. The watch shows time in binary since doing so requires less LEDs to display time than the usual watch patterns, driving the cost down.
Designing and Building a binary clock- [Link]