Stand alone GPS units (Honeywell HT9100, for example) can provide quite accurate winds aloft data, however, as has been mentioned, to use that data to make a decision about whether to land (or not) would be quite foolish....I personally have noticed wind data to show a tailwind of 100 knots (approximately) at 200 feet, when in actual fact, there was no such wind....otherwise we would have been truly in the weeds at the far end (not a happy thought)...
