The anemometer in my 1-wire weather station has a reed switch and a magnet. The roughest part to solve is having a GOOD bearing on the spinning element that will stand up to the elements year in year out.
It looks like I count 2 pulses per revolution... I'm not sure you need something more complicated. A mouse interrupter would provide way more sensitivity than you need if you want to count revolutions that translate to Miles per Hour wind speed.