An apparatus and method may operate to mount one or more communication assemblies relative to the exterior of a casing being placed in a borehole. Two communication assemblies can be placed in longitudinally spaced relation to one another along the casing, wherein each communication assembly is configured to obtain excitation responses from electrodes of a fluid sensing component, where the excitation responses vary based on properties of fluids in one or more regions of the annulus surrounding the casing. Additional apparatus, systems, and methods are disclosed.