  The dynamical scaling of quantum critical systems in thermal equilibrium may
be inherited in the driven steady-state, leading to universal
out-of-equilibrium behaviour. This attractive notion has been demonstrated in
just a few cases. We demonstrate how holography - a mapping between the quantum
critical system and a gravity dual - provides an illuminating perspective and
new results. Non-trivial out-of-equilibrium universality is particularly
apparent in current noise, which is dual to Hawking radiation in the
gravitational system. We calculate this in a 2-dimensional system driven by a
strong in-plane electric field and deduce a universal scaling function
interpolating between previously established equilibrium and
far-from-equilibrium current noise. Since this applies at all fields,
out-of-equilibrium experiments no longer require very high fields for
comparison with theory.
