The Polar RS800 training system gives runners and serious endurance athletes the most complete heart rate-based training solution yet. Taking the system a step further, the G3 sensor is a compact and lightweight GPS module that talks wirelessly to the RS800 system, enabling speed and distance measurement for a multitude of sports including cycling, Nordic skiing, in-line skating and kayaking. The addition of the G3 sensor makes the RS800 the most comprehensive planning and analysis tool for athletes who train across multiple disciplines.