A feature extracting unit obtains sensor data from a plurality of sensors to calculate each feature. When an event determining unit determines the occurrence of an event based on each feature, a display data constructor generates remote-controller display data for displaying the event. When an infrared sensor detects an abnormality, a microwave sensor whose power consumption is small after the infrared sensor is turned ON. When the microwave sensor detects an abnormality, a video camera and a microphone are turned ON, and the microwave sensor is turned OFF. A communication unit wirelessly transmits an image signal captured by the video camera and an audio signal processed by the microphone. Then, if the infrared sensor does not detect an abnormality, the video camera and the microphone are turned OFF.