It's a very good question, so lets firstly explore the reasons for having a moisture meter, then discuss whether you really need one.
Why a moisture meter?
The main reason for having a moisture meter is to get an accurate reading of the actual moisture content of your logs. I'll talk a little later about accuracy! It is all too often that customers think there wood is dry enough because their supplier said 'its been seasoned for 2-3 years' but does that mean its dry - no certainly not.
How to use a moisture meter
You can just measure the outside of the log, measuring across the grain of the split surface, but ideally you should split open the log with an axe to measure the internal moisture and take an average of the two readings. As long as the average is no more than 25% then that means your logs are ready to burn.
Types of moisture meter
There are many different types of moisture meters now being sold on the market and prices range from £16 - £50, but be aware that these will not be that accurate particularly if the wood is out of the 20-30% moisture range. We actually use a much more expensive type for our testing and this provides us with a far more accurate reading.
Who needs one?
Most importantly anyone that deals with wood fuel, stove installation or chimney sweeping should definitely have one, and if they haven't, I would ask why. How can anyone say that your wood is properly dry without some form of measurement at least to give you a guide.
Other ways to gauge moisture content
There are few ways to get a good idea of moisture content. Firstly if you look at the ends of your logs, dry wood will have good cracks appearing and the bigger the gaps the drier the wood. Secondly if you knock two logs together, you should get quite a hollow sound. If the wood is damp, it will give a dull thud! Finally if you are burning wood and the stove glass goes black, then most likely this is because your wood is not dry enough to the core.
So, in summary, if you are looking to season your own, or buy from your local supplier I would definitely get a moisture meter to keep tabs on things - don't take anyone's word for it, unless you buy HETAS approved kiln dried logs, in which case you should have ready to burn logs every time.