Sensing device for a nappy

A combined nappy and sensing device comprising:

• a nappy;
• and
• a sensing device comprising:
• an expandable member comprising one or more elastic elements extending between a plurality of attachment points, wherein the attachment points are configured to fixedly attach the expandable member to an external surface of the nappy, and wherein the one or more elastic elements are configured to stretch as the attachment points move apart such that the expandable member is configured to expand in accordance with expansion of the nappy;
• a detector unit coupled to the expandable member, wherein the detector unit is configured to detect expansion of the expandable member, and is further configured to determine a nappy fullness parameter based on the detected expansion of the expandable member;
• and
• an electronic control and power supply unit configured to power the sensing device;
• and
• wherein the attachment points of the expandable member are fixedly attached to the external surface of the nappy.