Some years back I had to have surgery, and during the hospital stay it was determined I need to occasionally monitor my heart. I was told to obtain a Kardia device.
A Kardia device works via an app. Physically, it is a flat device just a few inches long, and about an inch high. Once the app is activated it is operated by placing two fingers from each hand on the small metal surfaces, one hand on each metal surface. It takes about thirty seconds to get ready, then a clock counts down another thirty seconds. An ekg graph appears on the screen of your smart phone. This can later be downloaded by your physician, or the output can be emailed to your physician. The device gives a short analysis, and also records the heart rate. It is limited, and cannot detect a heart attack, but it can be helpful as a portable heart monitor. It easily fits in a pocket or purse.
There is also a service, for a fee, to have a physician read the output.
Now, a more elaborate version is available. As with most things, newer versions have improvements over the older ones.