Another alternative is a digital thermometer with a humidity reading for about 12 dollars. Know what the humidity is around your bow wood and you will know what the moisture content will eventually be. Here is how you figure it out....
http://www.woodbin.com/ref/wood/emc.htm But all you really need to know is this: At normal temps...
humidity MC
30pct - 5pct
43pct - 8pct
55pct - 10pct
65pct - 12pct
75pct - 14pct
Just another option to consider. The only draw back is you won't know exactly WHEN it's dry enough. I get my staves to the floor tillering stage and control the humidity for a couple weeks, then I proceed. No problems yet.
I don't have a drying box, but I bet a humidity meter mounted in a drying box would be the cat's meow.