The invention refers to an exchangeable power-supplying unit (200, 300) arranged to supply electric power to a device (100, 400). The power-supplying unit (200, 300) is arranged so as to provide the device (100, 400) with one or several additional functionalities and it can preferably be attached so as to form an integral part of the device (100, 400). The additional functionality is accomplished by one or several processing units (220, 312, 319) contained in the power-supplying unit (200, 300) for pre-processing information, which is subsequently communicated from the power-supplying unit (200, 300) to the device (100, 400).