Ask HN: How to approach marketing a geographically-based app

How does one solve the chicken/egg problem with geographically relevant apps like Tinder? I've read how Uber offered their services to private car companies. The app I'm building only works for people within a certain distance. But it doesn't offer a physical service like Uber where I can piggyback off of an existing market/service. An online campaign wouldn't necessarily work since users are spread far apart. The last thing I want is users to try my app out, find nothing there, then immediately uninstall it, much like I've done with all geo apps I've tried.

How does one coordinate launching/marketing in different cities over time while an app is available to everyone on an app store at the same time?