Most chest strap monitors send data to another device. This can be a smartwatch, fitness tracker, or smartphone. Many of them connect using Bluetooth or ANT+. Once connected, you can see your heart rate in real-time while running, cycling, or working out. Many people think that smartwatches or wristbands are enough to track heart rate. But those devices often use light sensors, which can give wrong readings during intense activity. On the other hand, a chest strap HR monitor stays close to your heart and picks up signals more accurately.