There’s an emerging marketplace for an Uber approach to medicine. Several startup companies, including Doctors Making House Calls (North Carolina), Pager (New York City), Heal (Los Angeles), Go2Nurse (Chicago and Milwaukee) and MedZed (Atlanta), are enabling patients to have a doctor or nurse come directly to their homes at the flick of an app. The on-demand approach to medicine is still in its infancy and there are signs it is converging with traditional medicine, not breaking away from it. The sector’s oldest company, Medicast, founded in 2013, recently abandoned its direct-to-consumer model in favor of collaborating with large hospital networks. The company recently helped Providence Health & Services — a medical system in the Pacific Northwest — launch its own house call app for the Seattle area.