Every once in a while the WPI gauge conversation comes up. If you're a spinner, you probably know what I mean. Someone asks about the necessity of it, almost everyone says no and tells them what they use instead. Personally, I use a ruler.
One thing that seems consistent is that people wrap the yarn to measure WPI--in which case, I'd think something with a larger circumference/perimeter that a lot of the alternatives to the WPI gauge would actually be a better choice.
I don't wrap. I shove my ruler into the hank and choose a variety of threads to measure with because I want something closer to an "average" WPI rather than the WPI of just one section, which is what you get when you wrap around a ruler or dowel or whatever it is you're wrapping it around. In fact, I'd go as far as to say a niddy noddy (or your skeining tool of choice) seems like it would make a better WPI gauge than a WPI gauge. I suppose if I were more anal about my spinning and consistency, wrapping would be a more attractive option, but I'm fine with my natural variation, so there will be a ±1 weight variation from what my intended yarn weight is at some point in the yards upon yards I'm spinning, especially since I stretch my projects out timewise.
So there you have it. I apparently think the best time to measure WPI is during the skeining process. But maybe that's just me.