I knew I saw a watch with a GPS system. However, 
  it is not a mapping watch. It is a running, hiking, biking etc,. watch made by 
  Timex with a Garmin GPS. It will track your mileage and speed as well as take 
  a heart rate and count laps. I don't see why you couldn't use it for training 
  mileage on horses as well. I think it is pretty cool. It is priced around 
  $200+.  Nike is also making watches that tell distance and speed (97% 
  accurate) and offer a few different prices. 
   
  The prices will drop. Last year I looked for 
  personal DVD players for the kids for our trip out west. They started at $599. 
  Now Wal-Mart is selling them for $199.
   
  Lisa Salas, The Odd farM
  School is out and I reeeeeally need those long, 
  hot insufferable rides just to make the rest of the summer seem bearable. I do 
  love my kids.... really. ;}