If this really was a "continuous electrocardiograph" it would be a game changer, but it measures "electrical activity of the heart using two fingers on either side of the device." Maybe they have other versions that don't require that which would be really cool, but if you have to do this, it can't be continuous because no one will be doing that continuously.
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Realtime medical tracking enables many things, let's hope the FDA's red tape doesn't kill it or delay it very long. Perhaps one band on one side with the watch and something else (a 2nd band?) on the other wrist or elsewhere.
It's also worth noting that this (like the Kardia) is a one-lead rather than a twelve-lead EKG. It's fine for assessing heart rhythm, but for the other major use of EKGs (detection of cardiac hypoxia or early signs of heart attack) it's not going to be terribly useful. A third (!) sensor would be needed for a 6-lead EKG.