In this article, the conception, design, and implementation of a discrete extended Kalman filter and a Takagi–Sugeno observer are introduced, and an innovative model description of an embroidered heater structure is presented. The observers are compared based on the algorithm complexity with the indicator of the number of arithmetic operations and the parameter error of the textile-based heater structure for health monitoring through virtual sensing. The proposed schemes allow an estimation of the heater temperature to guarantee safety by preventing overheating without a direct measurement. An estimation strategy is necessary because measurements of the temperature of the whole heater structure are usually not available, but this knowledge is vital for health monitoring purposes or for a safe shutdown if necessary. A cascaded sliding-mode control strategy using an integral surface for the electrical current and the temperature is presented. Measurements validate the utilized model. The effectiveness of the observers is justified by hardware-in-the-loop simulations and measurements.