Rob outlines several methods for the inspection of exterior cladding.
There are two basic types of meters: those with pins that you shove into the test material ("pin meters") and those that are moved across the surface of an EIFS, much like a clothes iron ("scanning meters"). Pin meters give an actual moisture percentage reading. They need to be used with care because they do not work on all types of materials. For example, they aren't much good with insulation but do work on wood products. Most pin-style meters have short pins that stick out of the meter's housing. For EIFS, you'll need a meter that has a cable with a remote set of long pins.