  We calculate interspecies Rydberg-Rydberg interaction strengths for the heavy
alkalis Rb and Cs. The presence of strong F\"orster resonances makes
interspecies coupling a promising approach for long range entanglement
generation. We also provide an overview of the strongest F\"orster resonances
for Rb-Rb and Cs-Cs using different principal quantum numbers for the two
atoms. We show how interspecies coupling can be used for high fidelity quantum
non demolition state measurements with low crosstalk in qubit arrays.
