TrailRunner - Mac OS X route planning and training software for Garmin GPS or Nike+ SportBand
ProfHacker: Using a Garmin Forerunner 305 as a Training Tool
Wrist-mounted GPS offers real-time training
The Garmin Forerunner 305 GPS unit with heart rate monitor. You can keep tabs on how hard you're working, making sure to neither over or under exert yourself. (Photo by Walter Cruz/Dallas