A study of a miniature microwave radiothermograph that can be installed on a person's body and measure the microwave radiation of internal tissues in the process of his vital activity to visualize the internal temperature is presented. Unlike the well-known radiothermographs, the measurement results of the developed device do not change when the impedance of the studied biological tissues changes. The use of a new scheme for constructing a balanced zero radiometer with two matched loads mounted on a Peltier element and using a chip for post-detector signal processing made it possible to create a miniature highly stable radiothermometer. The measurement error of the radio brightness temperature of the device weakly depends on the ambient temperature and on the device's own temperature. A detailed description of the design of a miniature radiothermograph with a conformal antenna array is presented. After the introduction of autonomous power supply and wireless communication with a smartphone, the proposed radiometer can be used as a wearable device for monitoring the temperature of internal tissues during human life, including in Earth orbit. In the future, the device can be implemented in a monolithic design, provided that the increased requirements for reliability and resistance to external influences imposed on microcircuits used in Space are taken into account. The creation of miniature microwave radiothermographs with a conformal antenna array measuring the microwave radiation of biological tissues opens up the possibility of monitoring the functional state of the human body in extreme living conditions.