Some of the best heart monitor devices for training no longer need the person to wear a chest strap. Manufacturers like Mio, which uses “Led” light to measure the pulses of the blood flowing in your wrist in order to get accurate readings. Other manufacturers like Garmin, Polar, Suunto, Tomtom, and Omron use their own software to monitor your heart rate in real time and then pass the data to your smartphone or other devices via an app.