Devices known as “wearables” are in fact tiny computers housed in your smartwatch or fitness wristband that track metrics such as distance walked or run, calorie consumption, and in some cases even your heartbeat.

Created by companies including Apple, Samsung, Fitbit, and Garmin, wearables are one of the hottest trends in healthcare technology.

In 2018, Apple garnered headlines with FDA approval for its ECG app for the Apple Watch, which acts as a mobile electrocardiogram that can monitor for heartbeat irregularities.

Likewise, Fitbit made waves in March 2019 for being selected as the first wearable company to provide information to the National Institutes of Health’s “All of Us” project, a million-person health database.

What these devices measure is resting heart rate. When you are at rest, your heart is pumping the least amount of blood required to supply oxygen to the body.

A normal resting heart rate is 60 to 80 beats per minute. Anything well above or well below that range may indicate a problem (though athletes can have a slower heart rate).

For instance, in elderly people, a very low heart rate could indicate bradycardia, a condition that can cause shortness of breath, fatigue, and even dizziness and fainting.

In addition, wearables can pick up potentially fatal heartbeat irregularities. By monitoring this information, wearable devices can diagnose heart problems outside the doctor’s office.