The U.S. Food and Drug Administration has given the KardiaBand its stamp of approval, AliveCor announced Thursday. The device is the first FDA-cleared personal electrocardiogram accessory designed for use with an Apple Watch. The KardiaBand allows users to take EKG readings in order to distinguish between normal sinus heart rhythms and atrial fibrillation, the most common type of serious heart arrhythmia, which can lead to strokes or other heart-related problems. The KardiaBand can record an EKG in just 30 seconds.