  We review the non-perturbative theoretical framework set up recently to
compute the inelastic scattering cross section from quantum impurities [G.
Zar\'and {\it et al.}, Phys. Rev. Lett. {\bf 93}, 107204 (2004)] and show how
it can be applied to a number of quantum impurity models. We first use this
method for the $S=1/2$ single-channel Kondo model and the Anderson model. In
both cases, a large plateau is found in the inelastic scattering rate for
incoming energies above $T_K$, and a quasi-linear regime appears in the energy
range $0.05 T_K < \omega < 0.5 T_K$, in agreement with the experimental
observations. We also present results for the 2-channel Kondo model, the
prototype of all non-Fermi liquid models, and show that there half of the
scattering remains inelastic even at the Fermi energy.
