The invention concerns a system for monitoring an occupancy area (15.1 15.3). The system includes the following elements. A device (10) that is arranged in connection with the monitored party (A D) which device (10) includes localizing means (12), means of communication (13) for communication in a wireless data communication network (20.1 20.3), a processor unit (MCU) and a storage medium (16), wherein at least location information (23 25) defining the limit of the said occupancy area (15.1 15.3) is arranged, based on which the current status information of the monitored party (A D) is adapted to be defined. A terminal equipment (22) that is arranged in connection with the monitoring party (21), and a wireless data communication network (20.1 20.3) as a means of communication between the said device (10) and the terminal equipment (22). The said location information (23 25) defining the occupancy area (15.1 15.3) is arranged for definition by the device (10), whose processor unit (MCU) is adapted to define the status information of the monitored party (A D) at each time based on the current location information defined by the localizing means (12) and on the location information (23 25) arranged in the storage medium (16) and defining the limit of the occupancy area (15.1 15.3), and wherein, according to a criterion established for the said status information, the device (10) is adapted to transmit to at least one piece of terminal equipment (22) information in a form established by its means of communication (13). The invention relates also to the device (10).