Telemedicine services, which allow doctors to treat patients via video, are gaining acceptance among consumers and insurance companies as it becomes clearer when a virtual visit is appropriate, industry executives say. Telemedicine has been more widely offered over the last five years, promoted by health plans such as Cigna Inc. and New York-based insurance startup Oscar Health. As many as 15 million people used the services this year, up 50 percent from 2013, according to the American Telemedicine Association.