Wearable technology is a more than $21 billion market and is on track to reach nearly $35 billion in the next four years. Smart watches are driving the trend. Apple is launching two new Apple Watch features Thursday for heart health. Norah O'Donnell met Apple COO Jeff Williams and vice president of health Dr. Sumbul Desai to learn how the Apple Watch is tracking atrial fibrillation, a disorder that affects at least 2.7 million Americans. Cardiologist Dr. Tara Narula also joins "CBS This Morning" to weigh in on the new features.