Cities are far from obsolete. They have been an obvious driving trend since industrial revolution. Why?

Short answer: money.

Cities are where the jobs are at. Long tail effects, Minimised infrastructure costs(transport, communications, power, etc). In industrialised nations there are minimal jobs outside of cities. Farming, mining, fishing, forestry, energy are about the only significant jobs outside of cities, and a non trivial portion of those workers are transported in from cities. As sucktastic as may be living in a city slum, its better job opportunity for the sustenance level people.

If cities didn't offer jobs- people wouldn't live in them. Cities are big and will continue to be big and keep getting bigger.

Product placements are mostly ok in my books. Why? The ad is providing or trying to provide entertainment. That is they give you something in exchange for viewing it.

Adds that take away value are the sucktastic ones. Such as the circle jerk adds of old(close one dozen more open type $%^$%.

Local magnetic field problematic(within low hundreds of meters)? yes.
In the middle of the ocean where submarines cruise, not so much. The closer they go to an anomaly(concentration of ferrous material) the worse it will be (inverse square law and all that).
Earth field stable enough: majority of the time, yes. One exception magnetic storm- but those can be forecast to some degree.

To counter problems they need inertial trackers in additionally. Better yet multiple units so they know when they are close to a magnetic anomaly.

Example similar consumer unit: CH Robotics um6.

Relevant knowledge: I have done surface(ground) magnetic surveys.

The common name you would be looking for is: Parallel hybrid electric. Except you are trying to run it without batteries/super caps which would have start, stop and burst issues others have mentioned.

The most common variant of this is the diesel-electric engine context: train,

For more information about advertising in the modern age look up Age of Persuasion. I attempt to listen in whenever I remember its on, because this program offers an amusing and informative perspective of advertising. And as the programs slogan states, we live in the Age of Persuasion.