A moving service that relocates a recurring argument from the room where it always happens to a room where it's never been allowed.
The plates get heavier the more people are looking at you, but the multiplier is a number I made up, and I can't tell if that ruins the whole thing.
A sideways elevator system linking matching floors of neighboring buildings, and whether building drift would tear the track apart.
Mail addressed to places that haven't been built yet, held until they are — and the awkward question of when a possible address stops being possible.
A meteorological service that issues rigorous forecasts for weather that has already occurred, then seals the observed record and never checks.
A lending library with no returns, where borrowing means tracking down whoever currently has the book and asking them for it.