Purchase Sierra Infinity and spend a few minutes with it. You'll find that a modest elevation change of 1000-2000 feet has very little effect on the bullet to 600 yards. Air density virtually the same, punch in the numbers and see the results! Changes in velocity due to temperature are the most critical thing a shooter needs to watch, especially when shooting past 600 yards.
Kestrel and Skymate both make good wind meters, but as the gentlemen mentioned they only tell you the wind speed at your location. You'll need to watch trees, grass and other environmental indicators between you and the target.
Its hard to beat experience!!!!
Hope this helps?