So you would like to build a wearable device that notifies you when the International Space Station is flying overhead? ISS Pin is a project from Adafruit that lets you do just that. It consists of a Particle Photon microcontroller and an Adafruit Neopixel ring.
The pin displays an orbiting white light when nothing is happening. It turns blue, white, or red when there is any activity. IFTTT was used to complete this project.