There is no better way to learn about electronics and wearables than creating your own. Adafruit has published a guide that shows you how to build your own GPS Dog Collar. This wearable device lets you track how far your have walked with your dog. You are going to need an Atmega32u4 Breakout Board, Adafruit Ultimate GPS Breakout, 1 x monochrome 128×32 OLED graphic display, and a few other parts to get started.
You can find out more information about this project on Adafruit.