I also have rattling around in my field box an old-school Dwyer Wind Meter. This analog device always works, needs no batteries, stays in calibration and is very robust. Prices though, are all over the map but here is the lowest cost I could find.
http://cspoutdoors.com/dwyerwindmeter.html
If all you want to know is the wind speed, that is definitely the way to go, really no reason to spend any more.
What most people quickly find is that they are overestimating the wind speed drastically. 10 is a fair bit of wind for stunt planes, 15 it starts to get challenging, and 20, you better know what you are doing. Anything anyone ever said about flying with no problem in 25 or above is, uh, (to be charitable) an over-estimate.
The most velocity I have ever flown in was around 22-25, gusting to 30 at times. That was the 2003 NATs, and a WAM contest at Del Mar High School in maybe 1987 they were about the same. It was close to that at the 95 NATs at times but without the gusts.
The very worst conditions I have flown in, however, it was about 15 MPH or so at the second Dayton Buzzin' Buzzards site down by the river. I wasn't nearly as skilled as I am now, and my equipment was nothing like as good, but when I lost control multiple times just flying around level, and ended up folding the stab trying to keep from crashing in inverted flight, I don't think skill was the problem.
Brett