A system comprising: a sensor array comprising a plurality of sensors each arranged to monitor a current position of one or more parts of the user's body; a plurality of aerial vehicles (101, 102, 103, 104), each one of the plurality of aerial vehicles having disposed thereon a respective one of the plurality of sensors; a sensor array controller configured to reposition the plurality of aerial vehicles so as to provide a line of sight between each of the plurality of sensors disposed on one of the plurality of aerial vehicles and a respective part of the user's body monitored by said one of the plurality of sensors; a physical feedback mechanism for providing physical feedback to the user, the physical feedback mechanism being configured to be worn on the user's body; a plurality of location sensors (901, 902) distributed over at least part of the user's body, each of the location sensors being configured to provide information on a current location of a respective surface of the user's body; and a controller configured to determine a current position of the user's body based on information obtained using the plurality of sensors and the information provided by the plurality of location sensors, and to control the physical feedback mechanism to provide physical feedback to the user in dependence on the determined position of the user's body, wherein the user's body may comprise visible surfaces and occluded surfaces depending on the current position of the user's body and a current spatial arrangement of the plurality of sensors disposed on the plurality of aerial vehicles, the visible surfaces comprising parts of the user's body visible to one or more of said plurality of sensors and the occluded surfaces comprising parts of the user's body hidden from view of said plurality of sensors, wherein the plurality of location sensors are disposed on at least two opposing surfaces of the one or more parts of the user's body, such that when one or more of the opposing surfaces is an occluded surface the controller is configured to determine the current position of said part of the user's body based on the information provided by said location sensors, and to determine the current position of any visible surfaces based on the information obtained using the plurality of sensors disposed on the plurality of aerial vehicles. a sensor array comprising a plurality of sensors each arranged to monitor a current position of one or more parts of the user's body; a plurality of aerial vehicles (101, 102, 103, 104), each one of the plurality of aerial vehicles having disposed thereon a respective one of the plurality of sensors; a sensor array controller configured to reposition the plurality of aerial vehicles so as to provide a line of sight between each of the plurality of sensors disposed on one of the plurality of aerial vehicles and a respective part of the user's body monitored by said one of the plurality of sensors; a physical feedback mechanism for providing physical feedback to the user, the physical feedback mechanism being configured to be worn on the user's body; a plurality of location sensors (901, 902) distributed over at least part of the user's body, each of the location sensors being configured to provide information on a current location of a respective surface of the user's body; and a controller configured to determine a current position of the user's body based on information obtained using the plurality of sensors and the information provided by the plurality of location sensors, and to control the physical feedback mechanism to provide physical feedback to the user in dependence on the determined position of the user's body, wherein the user's body may comprise visible surfaces and occluded surfaces depending on the current position of the user's body and a current spatial arrangement of the plurality of sensors disposed on the plurality of aerial vehicles, the visible surfaces comprising parts of the user's body visible to one or more of said plurality of sensors and the occluded surfaces comprising parts of the user's body hidden from view of said plurality of sensors, wherein the plurality of location sensors are disposed on at least two opposing surfaces of the one or more parts of the user's body, such that when one or more of the opposing surfaces is an occluded surface the controller is configured to determine the current position of said part of the user's body based on the information provided by said location sensors, and to determine the current position of any visible surfaces based on the information obtained using the plurality of sensors disposed on the plurality of aerial vehicles.