Make own remote temperature/humidity sensor

You can buy remote Oregon sensor THGN123N for about $20 or you can built your own temperature/humidity wireless sensor that implements Oregon protocol V2.1 for about $9 and have fun! First of all, we need accurate temperature/humidity sensor to check the weather outside. In my previous project the sensor si7021 has shown perfect results, so i recommend this sensor one more time: it has great accuracy, small form-factor and low power consumption. Second, we need mobile platform with low power requirements that can run on the batteries for a long time. Again, in the previous project such a platform has been successfully built. We can use atmega328p-pu chip, running at 1 MHz. The power consumption of this system is about 5 micro Amps! Third, we need the software library for sending the signals using appropriate protocol. This library is based on the software created by Domonique Pierre, the author of software, emulated Oregon V2.1 protocol.”