One scheme to reduce vessel activation during the early phase of ITER is to use helium as the heating neutral beam species. The diagnostic exploitation of deuterium heating beams is well established yielding, for example, ion temperature profiles, plasma rotation, impurity concentration, Zeff and beam penetration measurements. However the use of helium rather than deuterium gives rise to a number of concerns regarding the diagnostic prospects of such a change - limited experience with fast helium beams compared to the extensive use of deuterium systems and an uncertainty in the fundamental atomic data. We build upon a recent series of experiments with helium beams in JET to address these issues and to make predictions for ITER scenarios.