  Recent high energy gamma-ray observations (E>100 MeV) of blazar AGN show
emission spectra with no clear upper energy cutoff. AGN, considered to be
possible sources for the highest energy cosmic rays, may have emission
extending well into the VHE (very high energy, E>100 GeV) domain. Because VHE
gamma-rays are absorbed by pair production on the intergalactic background
radiation, much of this emission is not visible. Electromagnetic cascades
initiated by absorbed VHE gamma-rays, however, may be observable. Since the
velocities of e+e- pairs produced in a cascade are likely to be isotropized by
an ambient random magnetic field, extended ``halos'' (R>1 Mpc) of pairs will be
formed around AGN with VHE emission. Cascade radiation from these pair halos is
emitted isotropically and is observable below a few TeV. The halo radiation can
be distinguished by its characteristic variation in spectrum and intensity with
angular distance from the central source. This variation depends weakly on the
details of the central source model, e.g., the orientation and beaming/opening
angle of an emitting jet. Limiting or determining the intensity of the pair
halo can thus serve as a model-independent bound on or measure of the VHE power
of AGN. Next-generation Cherenkov telescopes may be able to image a pair halo.
