IoT security device

A security response device 100 comprises a security threat sensor 120 for detecting a security threat and a cellular modem 110 for establishing a connection with a remote station (50,fig.1). The device 100 is operable in a power saving mode in which the communications capabilities of the cellular modem 110 are inhibited. In the power saving mode, the device 100 is capable of detecting security threats but not performing communication functions. Detection of a security threat causes the device 100 to exit the power saving mode and enter a communications mode. In the communications mode, the device 100 is capable of sending a security threat message to the remote station (50,fig.1) and receiving a security response action instruction in response thereto. In response to receiving a security response action instruction the device 100 is arranged to perform that action via an alarm output actuator 130. The security threat sensor 120 may be a passive infrared sensor, a radar, a lidar, or a sonar. The security response action may be an audible or visible deterrent, or the emission of a substance or smoke. The device may further include a microphone 150 and camera 160 to gather information as to the nature of a detected threat.