Parisian Transit Real-Time Tracker (PWA)

Commuters need fast, offline-capable access to RER/train schedules without app store friction. This PWA provides real-time transit tracking for Paris with progressive web app advantages. Target users are Paris commuters and transit-dependent city residents.

RATP and SNCF both publish open APIs, and the official Île-de-France Mobilités app already handles real-time RER and train data with offline caching — so the "no app store friction" angle is a thin differentiator against a well-resourced incumbent with the same data source. The $200–1k/mo revenue band is realistic only through ads or a small tip-jar model, since commuters rarely pay subscriptions for transit data that's freely available elsewhere, meaning unit economics depend entirely on volume. PWA adoption momentum is real in 2024, but that's a technical delivery choice, not a moat. The most likely failure mode is that acquisition never scales beyond a few hundred users because discoverability for a city-specific PWA is poor without an app store listing, and word-of-mouth in a single metro area has a hard ceiling.