A pill thermometer is an ingestible thermometer that allows a person's core temperature to be continuously monitored. It was developed by NASA in collaboration with Johns Hopkins University for use with astronauts. Since then the pill has been used by mountain climbers, football players, cyclists and F1 drivers.
The Thermometer Pill is currently manufactured by the company, HQ Inc under the brand name CorTemp.
References
Pill thermometer Wikipedia(Text) CC BY-SA