Your wearable can now keep you from getting sunburnt, with the Flora digital UV index sensor. Adafruit took their popular SI1145 UV index sensor and cut out everything you don't need for using with a Flora. It's small, round, and connects to the I2C bus pads. Flora can even use Adafruit's library code to get calibrated light level and UV index data from the sensor.
Please note: This sensor can be used by Flora but is too complex for Gemma!
To use: connect the 3V, SDA and SCL, and GND pads of the sensor to your Flora 3V/SDA/SCL/GND pads, in that order. Then load up the Arduino library and example code from Adafruit's tutorial to your Flora.
Breakout Board details: