I can't imagine this being a hugely popular item, but it's certainly possible to get TV reception in the office or on a surface train if you are near a window and relatively near a broadcast tower. In a subway, signals can be repeated through leaky cable, the same way cell phone signals are done in many places and FM radio is done in some tunnels.

Usefulness is irrelavant anyway; I think the real market is people who have to have the latest toy, even if they are never going to use it.