Wearable devices are described herein including a housing and a mount configured to mount a contact surface of the housing to an external surface of a wearer. The wearable devices further include a coil disposed in the housing proximate to the contact surface and at least one sensor disposed on the contact surface and configured to detect one or more properties of the body of the wearer. The wearable devices are powered by a rechargeable battery disposed within the wearable devices. The wearable devices additionally include a recharger disposed within the wearable devices and configured to recharge the rechargeable battery using electromagnetic energy received by the coil. The sensor is disposed within a central portion of the contact surface enclosed by the coil.