The first module measures a few parameters : temperature, humidity, atmospheric pressure, and luminosity.

Temperature and humidity measurements are provided by a DHT11 sensor. However, i'm using the DHT11 mainly for humidity, as the temperature measurement are not really accurate. Temperature measurements will be handled by a DS18B20 later, as i found those to be more accurate and reliable.

Atmoshperic pressure measurements are provided by an adafruit BMP085 module (https://www.adafruit.com/products/391). This sensor is now discontinuated, and can be replaced by the BMP180 (https://www.adafruit.com/products/1603) with the same code, wirering, etc.

The light level measurements are provided by a light dependent resistor. However, i used this because i had a few, and had ADC pins left. Indeed, those sensors are not very accurate, and i don't really see how to translate  the measurements in lux. Those can however be useful in order to detect if it is dark or not.