  Protons can be plausibly accelerated to $\sim 10^{18}$-$10^{19}$ eV in strong
accretion shocks surrounding massive clusters of galaxies. Such protons
efficiently produce very high energy pairs through interactions with the CMB,
which then radiate synchrotron and inverse Compton emission with hard spectra,
peaking respectively in hard X-rays and TeV gamma-rays. We discuss the
prospects for detecting this emission from nearby clusters with current and
future facilities such as HESS and NeXT, which should provide a clear signature
of ultra-high energy proton acceleration and an important probe of magnetic
fields in the outermost regions of clusters.
