Abstract: A bed or chair exit sensing device to be placed in, on or in relation to a bed or chair, and adapted to detect a person leaving the bed or chair, comprising a piezoelectric sensor and a data processing device adapted to determine, by processing the signals from the piezoelectric sensor, when the person is leaving the bed, characterized in that the bed or chair exit sensing device comprises an accelerometer sensor, and said data processing device is adapted to determine bed or chair exit of a person on the basis of combined processing of the signal from said piezoelectric sensor and the signal from said accelerometer sensor.

Abstract: A bed or chair exit sensing device to be placed in, on or in relation to a bed or chair, and adapted to detect a person leaving the bed or chair, comprising a piezoelectric sensor and a data processing device adapted to determine, by processing the signals from the piezoelectric sensor, when the person is leaving the bed, characterized in that the bed or chair exit sensing device comprises an accelerometer sensor, and said data processing device is adapted to determine bed or chair exit of a person on the basis of combined processing of the signal from said piezoelectric sensor and the signal from said accelerometer sensor.

Abstract: A sensor device for an alerting system comprises a casing and a sensing element adapted to detect an alerting event, wherein said sensor device is adapted to output an alert signal in response to said sensing element detecting an alerting event. The sensing element is a photosensitive element adapted to detect, when said sensor device is positioned in a sensitive relationship to a display of a mobile communication device, an illumination of the display of said mobile communication device.