RCX5 G5 Heart Rate Monitor Watch. The Polar RCX5 Men's Fitness Monitor is excellent for triathletes, runners and endurance athletes. The sport profiles help you switch between different sports for accurate reports while the ZoneOptimizer coaches you at the right intensity. Cross the finish line in time with the Race Pace feature. The fitness monitor doesn't require a charge so it's always ready when you are, plus the battery lasts up to 8-11 months.