Even if permissions are enforced, there will be enough apps that most users will be willing to allow to track them, and those apps can participate in this progr

Even if permissions are enforced, there will be enough apps that most users will be willing to allow to track them, and those apps can participate in this program without being exactly explicit about it to the user. The apps' privacy policies will essentially be a bunch of legal mumbo jumbo amounting to "and you have no privacy", and users won't even bother to read that. Just because an uninformed user granted some app permission to track them, which app implied it could share that with LEOs, doesn't mean that the courts will consider warrant-less tracking this way constitutional. I don't know and can't predict whether the courts will or won't, but they well might not. There will be interesting cases arising out of this technology eventually. The SCOTUS has already said that police can warrantlessly use surveillance technology that is widely available to the public, but I doubt this tech will so become.