This UV monitor on hackaday.io was designed to help prevent UV-caused skin damage:
This is a UV monitor based around the SI1132 light sensor and an ATMEGA168. It uses a sound-based interface, where beeps signal settings for skin type and use of sunscreen, if any. This is to save the power and cost of a display, and also in recognition that the device will be used outdoors in bright sunlight, where only reflective displays would be usable.
SI1132 was chosen as it produces a ‘calibrated’ UV index and takes up very little space. ATMEGA168 was chosen as a cheap uC with hardware I2C support which is supported by the Arduino environment (to allow a broad range of users to easily modify the code as they see fit).
The design files and source code are hosted on GitHub:
matrixwide shared the board design on OSH Park: