"it's much more easier to force you to turn them off."

But of course they don't force you to turn them off. They ask you to turn them off. As I pointed out in my semi-joke about using them as a terrorist weapon, there is nothing preventing people from turning them on in their pockets.

And if someone DOES leave their gps or other device turned on, is there technology on the plane that would allow the authorities to find the culprit? I doubt it.