A method and a device for utilization of mobile radio telephones for surveillance and/or control purposes in which a radio unit (3) for reception of signals from mobile radio telephones is arranged to be activated in a first step by an incoming signal from a mobile radio telephone, as a second step analysing the first part of received signal with regard to the PIN/SIM number (or corresponding) and/or inputted call number during the handshaking procedure between the mobile radio telephone and an associated base station for comparison with preprogrammed corresponding information, and as a third step, when correspondence has been established, initiate preprogrammed procedures and/or actions, and if non-correspondence is established, return to "resting" and non-activated condition pending a signal inputted from a mobile radio telephone. The receiving radio unit (3) is preferably performing a scanner function in "resting" condition with regard to within the geographical area utilized frequencies for mobile telephones, and performs a locking operation to the frequency for an incoming signal, maintaining this locking when approval for the third step is established, and returning thereafter, as well as when non-acceptance is established during the second or third step, to "resting" function with scanning of the frequencies. The reception range for used radio unit (3) is preferably maintained restricted during the first and second step, and extended during the third step, whereby reception of called subscriber can be accomplished from the base station communicating with the mobile radio telephone.