The central unit of the server room monitoring system I implemented a Raspberry Pi device. An add-on card is connected to it, that ensures uninterrupted power supply for the Raspberry, it can operate from power supply and battery as well. The add-on card by the help of its sensors measures the ambient temperature, the battery voltage and whether the 230 V AC power is present. Raspberry by means of a radio module keeps communication with a remote card with a couple of sensors and an ATmega microcontroller on it, which takes care of reading their data out. The remote card is also capable of operating from external power supply and battery power too, measures ambient temperature and humidity, furthermore supplies information of its battery voltage. The management software of the system consists of several parts: the application running on the remote card microcontroller, the Raspberry management software, which collects data from the local sensors, keeps connection to the remote card and stores the sensor data in a MySQL database. The control software compares the measured values with the predefined limits, if any of the values gets outside, it sends an e-mail alert. The system also incorporates a WCF service, which provides data to the web visualization client and keeps in touch with the Raspberry management software via FIFO channels. The web client allows the user to display the measured data and changing settings.