The tunneling of spin-polarized electrons across a magnetic tunnel junction driven by a temperature gradient is a fundamental process for the thermal control of electron spin transport. We experimentally investigated the atomic-scale details of this magnetoSeebeck tunneling by placing a magnetic probe tip in close proximity to a magnetic sample at cryogenic temperature, with a vacuum as the tunneling barrier. Heating the tip and measuring the thermopower of the junction while scanning across the spin texture of the sample lead to spin-resolved Seebeck coefficients that can be mapped at atomic-scale lateral resolution. We propose a spin detector for spintronics applications that is driven solely by waste heat, using magneto-Seebeck tunneling to convert spin information into a voltage that can be used for further data processing.