I bought two actually, thinking they would be great tools to help me figure out when it's safe to fly. I used them a few times until I realized they were pretty well useless. I thought maybe they would tell me that I was being too cautious and would allow me to fly more often - nope. Wind can also be very 'gusty', so an instantaneous reading isn't much help.
I have had half a dozen 'UAV Forecast' type apps, they are all so wildly inaccurate that I have personally found them to be useless as well. Almost 100% of the time, they tell me the opposite of the conditions I am observing while actually standing there. Didn't matter where I was in the world (I travel a lot), they were so inaccurate it was comical - I got rid of them all.
As it turns out there is no better wind gauge than my own personal judgement (what I can feel, looking at treetops, leaves, water, flags, etc.), along with the knowledge that wind is usually much stronger a little ways up in the air and I need to be extremely cautious at all times. No issues to date (knock on wood) and I have less stuff to haul around haha.