I think what may be of interest to US racetracks would be the service provided by turftrax.com. They use satellite technology and electromagnetic induction scanning techniques to provide highly accurate soil moisture profiles. Their magnascan project started off as an aid to the farming community but they now scan around 12 UK racecources and put up the going profiles. In truth, I don't really have a clue how they do it, but it may be worth a look. Cheers.