• A Bluetooth Chest strap Heart sensor is the most reliable way to measure heart rate outside medical facilities

• A Bluetooth Chest strap Heart sensor is cheap to buy (<50 Dollars in any store) if the subject does not already own one bought before buying the HEART SENTINEL

• A Bluetooth Chest strap or wearable sensor as the Sensoria T-shirt Heart sensor is much more reliable than devices sensing the blood arterial pulse (if you disconnect them no pulse will be sensed and no differential diagnosis from cardiac arrest is possible by any means..this does not happen with the chest heart sensor, which actually senses heart rate from the heart's electrical activity

• A Bluetooth Chest strap Heart sensor is not always perfect either for heart rate sensing and rarely it can zero or sense artifacts, but the motion control of the HEART SENTINEL saves you from artifactual (false positive) alerts. Exercise=motion. This is why the HEART SENTINEL is designed only for sports and not for resting. The motion control, although only rarely needed in case of errors from the heart sensors guarantees from malfunctions.

• Modern era Bluetooth LE (low-energy) is battery conservative. In our field tests, an iPhone 6 could run the HEART SENTINEL for more than 7 sports hours without battery charging