Tobbera:
When I steer my boat upwind I use the tell tales in the Jib to keep a constant angle to the wind. To feed this info into the Arudino, my idea is to place the wind vane about a meter in front of the Jib, and a meter above the water, to get clear wind.
I am familiar with those tell tales - I had forgotten about them and I agree they are very useful, even essential. Unfortunately all they tell you is how well the wind is flowing over the sail. At that point the airflow is significantly affected by the sail and it is anything but "clear wind". If your wind detector is in clear wind in front of the sail it will be just as fickle as at the top of the mast.
Another thing to bear in mind is that the tell-tales are useless if the airflow over the sail stalls - they can't tell you where to steer the boat to get back into the wind. The wind vane could provide that information but probably can't deal with the fine control.
...R