Apple Watch is pretty great at measuring heart rate in my experience. Part of the difference may be the circumstances in which the measurement is taken—in the clinic, "resting heart rate" is typically measured when the patient is sitting, in a controlled setting.

For an app like Cardiogram, your heart rate is being measured throughout your day, "in the wild," every 10 minutes. We do filter out any measurements taken while you were moving (walking, during a workout) and for a few minutes after the movement stops.

But, of course, your heart rate might be higher in real life than it is at the doctor's office. Maybe you've just had coffee. Or you're stressed out driving in traffic. For example, here's mine in bay area traffic: https://twitter.com/bballinger/status/695704441626886145

In Cardiogram itself, we show the user their whole distribution of resting heart rates. What's reported in the blog post is the median of all those measurements.

By the way, I don't think it's known what the "right" answer is here. We do know stress can trigger a heart attack, and coffee can trigger arrhythmias like atrial fibrillation. So perhaps there's a lot of information lurking in the shape of your personal distribution of heart rates. But before now, nobody has really had the data to answer these types of questions.