UPDATE: adding a light sensor to the device.
The idea behind this project is connect some sensors to the Raspberry Pi and put the information available on demand via Twitter requests and put sensor history data online on the web
To do that, I used a DHT22 temperature and humidity sensor connected to the Rasberry Pi.
You can get all the detailed steps from Adafruit website
For more detail: Sending weather data via Twitter using Rasbperry Pi and DHT22