The Core Body temperature (CBT) is an important medical parameter. Although used in general medical applications as well as alpine sports it is barely used in other sports disciplines. This is because, to date, no non-invasive, permanent and cable free measurement of CBT has been possible. The newly developed technology earconnectTM makes it possible to measure the CBT permanently and wirelessly using the ear sensors cosinuss° One on the external auditory canal. The data collection for the validation of the CBT using Bland & Altmann took place at the German Heart Center in Munich during heart operations on 15 patients (n = 15, more than 10,000 data pairs), because these operations are accompanied by an artificial hypothermia to 32 degrees and a subsequent warming. In comparison, the ear sensor was standardized with a pulmonary artery catheter, nasopharyngeal temperature probe and urinary catheter. Once the ear sensor is properly placed, it can measure the CBT validly. Using an algorithm, it is possible to calculate the values of the CBT for invasive measurement methods (pulmonary artery catheter). This would be a huge step towards wireless operations.