I have been a dealer for Computech for a couple of years . I sell all of their products including hand held and trailer based remote weather stations. I had been using a different brand of W/S because I had bought it about 15 years ago. A couple of months ago I bought one of the raceair pro and started using it. I only had it for the last couple of races I attended this year but it looks like it will predict a lot better than what I had been using. The big difference in this one and the others is that you use your last good pass to predict your next run instead of relying on a database that may have been saved from a different day or track. This allows you to not only see how much the weather will affect your et but it will take into account other track conditions based on your most recent good run. montecarlo84 is dead on though, it will only predict well if the info you're using is good. Here's a link for the race air and race air pro. You can download the user manual to get an idea of how they operate.
http://computechracing.com/Product_G...-portable.html
If you're interested pm me and I can get you a price.