DHT22 Temperature and humidity sensor (AM2302)
http://www.vanallesenmeer.nl/DHT22-temperatuur-luchtvochtigheid-sensor-Arduino-
https://www.sparkfun.com/datasheets/Sensors/Temperature/DHT22.pdf
http://www.adafruit.com/datasheets/Digital%20humidity%20and%20temperature%20sensor%20AM2302.pdf