Dr. Eric Topol is only half joking when he says the smartphone is the future of medicine — because most of his patients already seem “surgically connected” to one.

But he says in all seriousness that the smartphone will be a sensor that will help people take better control of their health by tracking it with increasing precision. His book, “The Creative Destruction of Medicine,” lays out his vision for how people will start running common medical tests, skipping office visits and sharing their data with people other than their physicians.

Dr. Topol, a cardiologist and director of Scripps Translational Science Institute in La Jolla, Calif., is already seeing signs of this as companies find ways to hook medical devices to the computing power of smartphones. Devices to measure blood pressure, monitor blood sugar, hear heartbeats and chart heart activity are already in the hands of patients. More are coming.

He acknowledges that some doctors are skeptical of these devices. “Of course, the medical profession doesn’t like D.I.Y. anything,” he said. “There are some really progressive digital doctors who are recognizing the opportunities here for better care and prevention, but most are resistant to change.”