Corsa

Well yes, GPS devices are useful for runners too and this Garmin Forerunner 305 I believe is one of the best on the market.

What is it useful for? Very much so. First of all to understand the pace we are keeping at any moment without having any kilometer reference point. The only valid technology for this purpose is the use of the GPS system which provides us with very precise data on speed and elevation. There are devices on the market like the Nike+ for iPod, but being equipped only with an accelerometer they need to be calibrated and will never be so precise.