  The effect of impurities which induce local interlayer tunneling in bilayer
exciton condensates is discussed. We show that a localized single fermion bound
state emerges inside the gap for any strength of impurity scattering and
calculate the dependence of the impurity state energy and wave function on the
potential strength. We show that such an impurity induced single fermion state
enhances the interlayer coherence around it, and is similar to the
superconducting proximity effect. As a direct consequence of these single
impurity states, we predict that a finite concentration of such impurities will
increase the critical temperature for exciton condensation.
