A mobile functional apparatus is arrangeable on a body part of a user and includes at least one communication unit configured to communicate with at least one external unit and/or at least one sensor unit configured to capture at least one user and/or environment parameter. The mobile functional apparatus further includes at least one energy harvesting unit configured to convert at least one form of energy into electric power for supplying electric power at least to the at least one communication unit and/or to the at least one sensor unit.