Mark,
you can make a very cheap anenometer, out of a bike speedo. It's not wireless of course, you need to run a lead to the display. If you're interested I'll dig up the instructions

Unless you're in the open, a weather van will swing around more than that with turbulance of neighbouring roofs, mine does anyway.

I got one from Jaycar for my wife for christmas.It works great, and unlike most of the e-bay ones it keeps a record of the maximum and minimum recordings reached, (which you can reset once you've looked at them), so you can see how much wind you missed out on when you were off doing whatever you were doing instead of sailing.

Hi Mark - I recently bought a wireless wind station from La Crosse Technology (model WS3502). I haven't installed it yet so I can't vouch for performance but it has all the features I was looking for. Has wind speed in knots (some stations only read in kilometres per hour or miles per hour!) & wind direction plus barometer. No temperature or humidity. Shows max wind & various alarms etc. You can download to computer for history analysis etc. - software supplied. Remote unit runs on batteries or mains power when connected to display unit using cable supplied (uses standard RJ12 phone plugs). Purchased from the Weather Shop (Sydney 02 9679 0688) price $298 incl courier to Qld. Well worth a look on their website