Anemometer

Step outside the sprayhood.

Wet the forefinger of your right hand. Hold it up to the breeze. Feel what happens to it.

Observe the surroundings. Are dogs/people being blown off the dock? Are sheep flying horizontally past the stern? Are huge waves crashing against the harbour wall?

You now have all the information you need to decide whether or not to go sailing.

Please send 10% of the 45 euros I have just saved you to the RNLI.

Best wishes.
 
There are lots of hand held anemometers on e-bay, like this http://www.ebay.co.uk/itm/HANDHELD-...Sailing-Surfing-Weather-Station-/130653039074
I think most of them would do as good or better job than attaching something like that to a phone. You can get hand held ones with the cups, but they are easily damaged, so the fan blade type that need pointing directly into the wind are a better bet, if slightly less accurate.
 
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