All, Are there any "smart" defrost controls that can sense when a low temp evaporator needs to be defrosted?

It seems to me a air pressure differential system between the front and back of the coils could be used to trigger an as needed defrost cycle rather than simply using a regularly scheduled time clock.

In my case, the humidity loads on my evaporators can change significantly with production demands. If possible, I'd rather not pump heat into a freezer to defrost a unit if not needed.

Thanks!