Add to the dizzying number of Apple Watch accessories the first FDA-cleared medical device made for Apple's hot-selling smartwatch. KardiaBand is an Apple Watch strap that lets users capture their electrocardiogram (ECG) anytime by touching their thumb to an integrated sensor. Results are displayed on the face of Apple Watch and allow the detection of normal sinus heart rhythms and atrial fibrillation, the most common heart arrhythmia. KardiaBand sells for $199, about twice as much as its previous smartphone-based incarnation. Its manufacturer, Mountain View, California–based AliveCor, has also launched an Apple Watch app, SmartRhythm, that taps a deep autoregressive neural network using heart rate, activity and ECG data from healthy and sick populations and alerts the user to record an ECG if their heart rate differs from the neural network—for example, if it rises while they are resting, by comparing their heartbeat with the user's location and speed provided by the watch's built-in accelerometer.

Credit: alivecor