Fucking hell. This is exceptionally disturbing. This sort of service needs to be legally regulated now . The app devs must be required to warn in large block letters that evryhting you do in the app, even while offline, is streamed to some random company. You can argue all you want that "everyone's doing it", but it doesn't make this any less unacceptable and going against basic expectations of privacy.
I think you're overreacting. Privacy policy disclosure is obviously in order, but that's about all there is to it.
A reasonable person would assume that if an application has no functionality that requires sending data over the network, the application won't surreptitiously spy on you and send your data over the network.