The best wind sensor to predict the winds for kiting is found at iKitesurf.
Predicting the wind on Martha's Vineyard can be difficult as there are no really good south facing wind sensors. We like to use the Vineyard Haven Sensor as a basis of our prediction, then look at the local marine forecast and smaller sensors around the island to get a read on what the wind is doing.
Generally, if you see southwest winds in the low teens and building throughout the day, there is a thermal that will fill in the afternoon and you can get out on a big kite. You can generally add a few knots to the forecast to factor for the thermal effect.