This is very handy when shopping for rough cut lumber to make sure the piece you are selecting is dry enough for the area.
It is species compensated so much more useful than some of the others which can give you an idea of the change in moisture content but not absolute levels. The only thing I would change on it is to make the probes longer and allow it to be hammered into a piece of wood to get a reading more near the center, but it works fine for any 4/4 sizes.