The HRM-Pro Plus is ideal for both indoor and outdoor training providing heart rate, heart rate variability and running dynamics. Running dynamics requires a compatible Garmin smartwatch and include vertical oscillation, ground contact time, stride length, vertical ratio and more. This is truly an advanced heart rate monitor. Not wearing your watch? No problem. The HRM Pro Plus records steps, calories burned, intensity minutes and more even when you're not wearing your Garmin watch. Bluetooth technology makes it easier than ever to upload recorded data once you return to your compatible Garmin smartwatch. The HRM Pro Plus is small, lightweightand features up to 1 year of battery life. The tool-free battery door makes replacing your batter simple!