Discovering that a Bluetooth car battery monitor is siphoning location data
Phones already have app permissions: can access you contact, can access your location...But no major phone OS provides a reliable "can access the internet" permission (without jailbreak/root). This would solve this issue much above the stack. I can  install the dubious app. If the app can't access the internet at all (properly enforced by the OS) then by definition it can't leak anything.I find it particularly disappointing from Apple. If they were truly committed to privacy as they claim, this would be a feature already.