I have a pinless Wagner moisture meter. Pretty expensive but will tell you how wet the center of a piece of wood is not just the surface. I have had mine for 20 years and have had it rebuilt by Wagner lately when it gave up the ghost. A rebuild cost $99.
Do you need one, no, but they sure are handy. There is no telling how many times people gave me "seasoned" wood that I checked with my Wagner and found out it was still green.
I don't use the species scale to get exact reading from my wood. I put my meter on osage I know is well seasoned and use this reading as a base line for all the osage I check.
If you plan to stockpile a lot of wood I would get a moisture meter, if you are looking at making just a few bows I wouldn't spend the money.