There have been many ...

There have been many developments to the original Coulter Counter that may be amenable to such an application (ref. Ceramics, food production).  As yet none is commercially represented as an option.  I do see a potential problem in plugging or other inconsistencies when applied to an external inlet stream of varying composition instead of the relatively homogeneous (or at least, predictable) composition of the samples used for analytes in the medicinal and lab applications.