Had a JeeNode Lux Plug on a breadboard for a couple of weeks now. Jumper wires sticking out all over. So it was in due time to mount it in a more permanent manner.
The Lux Plug is a small board containing a TSL2561 chip, which connects to the I²C bus and measures incident light levels.
Two sensors are included, one is sensitive to infrared. An algorithm is used to calculate the light levels in lux, by combining the readings from both sensor types. The total measurable dynamic range is 1 : 1,000,000.
An I²C bus running at 3.3V is used for I/O, with all the power and signal lines brought out to both sides of the board to allow daisy-chaining with other I²C-boards. 3.3V almost screams ESP-8266 so an ESP-01 was selected for the microcontroller.
Found a nice plastic box and added a BMP180 barometric pressure sensor and an HTU21d temperature and humidity sensor just for fun. Both are happy to run I²C at 3.3v.
A DC step-down converter was added to convert the 12v from the power bus running through the house down to 3.3v