I don't usually write 500-plus words about a mobile app that most people outside of my city have even heard of. But this wasn't just any app.

The app that for more than seven years has stamped my smartphone as a D.C.-area device stopped working Saturday. But while I’ll miss having MetroHero on my phone, its utility will live on–not only in software built on its open-source code, but in an upcoming tool that Metro developed after learning from its example. MetroHero debuted Sept. 20, 2015 on Google’s Play Store as an app that would…