A system comprising a wearable device and a wearable sensor, each one being configured to be in communication with the other one when the wearable device and the wearable sensor are in contact, the wearable sensor when worn by a wearer is configured to measure data relative to the wearer, and the wearable device comprises at least:- a communication component configured to receive data from the wearable sensor when the wearable sensor is in contact with the wearable device, and- a power source for providing electrical power to the wearable sensor when the wearable sensor is in contact with the wearable device.
