We have covered a bunch of smart rings here in the past. They can help you unlock your gadgets and even track your activities. This Bluetooth Ring by bateske is a simple wearable device with a 64×32 monochrome OLED display and a touch button, allowing you to receive and reply to notifications from your smartphone. The battery life lasts 4+ hours with the display on.
The ring is powered by the NRF51822 chipset and has an ARM-M0 embedded microprocessor running at 16mhz. You can find out more information about it on arduboy.com.