  Holography grew out of black hole thermodynamics, which relies on the causal
structure and general covariance of general relativity. In Einstein-{\ae}ther
theory, a generally covariant theory with a dynamical timelike unit vector,
every solution breaks local Lorentz invariance, thereby grossly modifying the
causal structure of gravity. However, there are still absolute causal
boundaries, called "universal horizons", which are not Killing horizons yet
obey a first law of black hole mechanics and must have an entropy if they do
not violate a generalized second law. We couple a scalar field to the timelike
vector and show via the tunneling approach that the universal horizon radiates
as a blackbody at a fixed temperature, even if the scalar field equations also
violate local Lorentz invariance. This suggests that the class of holographic
theories may be much broader than currently assumed.
