The measuring is achieved using the emonTx v3 board (see the wiki). It is powered using a 9v-230v AC-AC adaptator which is recommended to get a best power monitoring accuracy, giving the real power consumption (which is what you get billed for).
Temperature and humidity are measured through a sensor and sent to the base station using RFM12B wireless modules (433 Mhz).
All the data (power, temperature, humidity) sent by the modules described above is gathered by a Raspberry PI board with the addition of an RFM12Pi expansion board (to be able to get the data over the wireless).
The data collected can :