I can see how this could be really helpful for coaches and things like that.  There have been quite a number of deaths over the past couple of years during practice from dehydration.  I guess the best option is to just make sure you are drinking water as much as possible.  I can be hard to tell just how bad it is when you have heat and humidity involved though.   Plus, you never know what level of hydration the players come to the field to start with.  Nice hunt!