Arduino library sensor receive signals used by WS8707 weather stations sensor, using remote 433MHz low cost module.
It also appears comparable with the weather station HAUS OH OH1000
Development can be read in http://domotica-arduino.es/foro/Thread-Integrando-WS8707-sensor-temperatura-humedad-en-Excontrol-Arduino
It may be compatible with the WS8426 (temperature only) More economical. I could not see if it's true.