Pebble watches used a Sharp transflective LCD MiP Memory in Pixel display, meaning that the back surface of the LCD was slightly reflective for daylight reading

Pebble watches used a Sharp transflective LCD MiP Memory in Pixel display, meaning that the back surface of the LCD was slightly reflective for daylight reading, with front lighting for night. Memory in pixel means that each pixel remembers its current state, saving on a lot of power budget because the bus/LCD controller is completely shut down, it essentially only uses power to update the display. Versus a traditional LCD or oled where you need to send it data at x refresh rate continously, meaning the high power draw bus and controller are constantly slurping power. Even though eink has gotten better I still wouldn't use it for something like this, the refresh rate is still a tad too slow, the controllers are always proprietary weirdness with crazy voltage waveform magic to clear the display properly, resulting in that ugly multiple flashing that most eink/epaper displays do.