A food thermometer includes a first portion for insertion into food. The first portion includes electronics sensitive to heat, and a third portion of the thermometer includes an antenna for transmitting data. According to one aspect, a completion time is estimated based on an ambient temperature and a rate at which the food temperature changes. According to another aspect, the thermometer includes an outer shell with a metallic portion and a non-metallic portion. An inner shell inside the outer shell extends from the metallic portion into the non-metallic portion such that the inner shell in the non-metallic portion serves as at least part of the antenna. The inner shell with the metallic portion of the outer shell serves as a coaxial transmission waveguide for an antenna signal.