  Any future high energy e+e- linear collider aims at precision measurements of
Standard Model quantities as well as of new, not yet discovered phenomena. In
order to pursue this physics programme, excellent detectors at the interaction
region have to be complemented by beam diagnostics of unprecedented precision.
This article gives an overview of current plans and issues for polarimeters and
energy spectrometers at the International Linear Collider, which have been
designed to fulfill the precision goals at a large range of beam energies from
45.6 GeV at the Z pole up to 250 GeV or, as an upgrade, up to 500 GeV.
