You can't remain secure against an organization that has effectively unlimited resources. All you can do is make it harder for them -- and that is most easily accomplished by non-technical means rather than a more advanced version of existing technical means.
A cheaper iPhone would be huge in a lot of developing countries, China most definitely included. There's already so much cachet around Apple products in major cities, but despite it becoming Apple's biggest market there just aren't that many people (percentage-wise) that can afford them.
Talk to people face-to-face, maybe?