The nodes use the Atmel ATtiny84 microprocessor and a HopeRF RFM12B transceiver module. Thus, they can be programmed using the Arduino IDE. They can be easily used with a DS18B20 digital temperature sensor, a dual temperature/humidity sensor, such as the DHT22 or an analogue temperature sensor such as the TMP36 or many other kinds of sensors.
They are powered using three AAA 1.5 V batteries. Thanks to some modifications, including a booster and the power-saving ATtiny84-PU microcontroller, battery life is now extended up to one year.
The receiver communicates with the Raspberry Pi though it’s serial port. Transmitted data can be recorded to a MySQL database by listening to the serial port using a simple Python script.
This open source project is very well documented in the German Raspberry Pi Forum where you can possibly sign-up for the next omnibus order. Arduino sketches and the PCB layout (Eagle-Files) can be obtained from github.