We investigate thin-film resistive thermometry based on metal-to-insulator transition (niobium nitride) materials down to very low temperature. The variation of the NbN thermometer resistance has been calibrated versus temperature and magnetic field. High sensitivity in temperature variation detection is demonstrated through efficient temperature coefficient of resistance. The nitrogen content of the niobium nitride thin films can be tuned to adjust the optimal working temperature range. In the present experiment, we show the versatility of the NbN thin-film technology through applications in very different low-temperature use cases. We demonstrate that thin-film resistive thermometry can be extended to temperatures below 30 mK with low electrical impedance.