The Kairos Smartwatch is a mechanical watch that has a transparent OLED on top. The OLED is a 1.4" (diameter) full color round PMOLED (40% transparent). The watch has an ARM Cortex M4 CPU (a model with an Intel CPU is coming too), a 180mAh battery (should be enough for 5-7 days as display won't be used to display the time), a 3-axis accelerometer and Bluetooth 4. It runs on Kairos' own smartOS (compatible with both Android an iOS) - but Android Wear OS will be available too.
Interestingly, Kairos says that they will also offer the same watches but with a different display: an icon-type transparent display that will only show static icons, numbers and text. This one will offer 60% transparency.