  Quantum probes are atomic-sized devices mapping information of their
environment to quantum mechanical states. By improving measurements and at the
same time minimizing perturbation of the environment, they form a central asset
for quantum technologies. We realize spin-based quantum probes by immersing
individual Cs atoms into an ultracold Rb bath. Controlling inelastic
spin-exchange processes between probe and bath allows mapping motional and
thermal information onto quantum-spin states. We show that the steady-state
spin-population is well suited for absolute thermometry, reducing temperature
measurements to detection of quantum spin distributions. Moreover, we find that
the information gain per inelastic collision can be maximized by accessing the
nonequilibrium spin dynamic. The sensitivity of nonequilibrium quantum probing
effectively beats the steady-state Cram\'er Rao limit of quantum probing by
almost an order of magnitude, while reducing the perturbation of the bath to
only three quanta of angular momentum. Our work paves the way for local probing
of quantum systems at the Heisenberg limit, and moreover for optimizing
measurement strategies via control of nonequilibrium dynamics.
