If you live in New York City or plan to visit the city at some point, you may want to download Subspotting, which is a WiFi signal tester specifically meant for the NYC subway system.
Simply put, the app "provides information about the available cell phone service and WiFi signals along all 21 lines, 469 stations, and 660 miles of track of the New York City Subway."
Furthermore, the information is laid out in a neat-looking fashion, providing some really cool visual effects, so if you're not getting a good WiFi signal, you can open up the app to see what station nearby has the best signal.
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