It is easy integrate DHT11 temperature and humidity sensor with Arduino Uno board. You can find enough resources in the web how to connect DHT11 with Arduino.
Measured temperature and humidity can publish to a Web via APIs supported by cosm.com.
You can find the working code in the Github.
When you upload the program to Arduino UNO board you may get an error saying
“Serial port ‘/dev/ttyACM0’ not found. Did you select the right one from the Tools > Serial Port menu?“
This error occurs when user do not have write privileges to device /dev/ttyACM0. User can fix this issue by giving enough rights to user or simply give all writes to the device. ( chmod 777 /dev/ttyACM0 [this is a hack ;)])