Wearable devices (100) capable of measuring a core body temperature and other vital signs of a user in a range of situations are described herein. The wearable device is arranged to be retained within the ear canal of the ear, in order to prevent the wearable device from inadvertently removing itself from the ear. Providing an infrared thermopile (101) at the innermost end of the ear insert ensures that the infrared thermopile is provided as close as possible to the tympanic membrane which will be used to provide an indication of the core body temperature. The device has an audio conduction channel (111) at least partly defined within an ear canal extending member (114), the audio conduction channel configured as a waveguide to conduct sound through a blocking member (212) to a distal portion of the ear insert.
