ZocDoc is a health-care-specialty application that has become a crossover hit on lists of popular apps, Dan Munro writes. ZocDoc is a "[W]eb-based service to help consumers find and schedule doctor's appointments online -- in real time," he writes. The app appears as No. 70 on Business Insider's Top 100 Apps for 2013 list. "[H]aving any health app appear on a relatively mainstream (i.e.: non-healthcare) list is definitely noteworthy –- and a solid indication of being able to engage consumers at scale with a cloud-based health service," Munro writes.