With the help of ferromagnetic Heusler alloys, which are mixed in powdery form into a cylindrical polymer sample surrounded by an induction coil, temperature can be measured. Some 10 K below the Curie temperature small temperature changes already yield considerable signals in the induction coil via the temperature dependence of the permeability of the alloy. From the tremendous variety of Heusler alloys avaialable for each temperature region of interest the proper material can be chosen. The amount of sample needed is small enough to leave the rheological properties of the melt unchanged. Measurements do not involve touching the sample and follow each temperature change more or less simultaneously since the grains of the alloys are very small and have very small heat capacities only.