That's already the de-facto situation on iPhones a lot of the time - you can set it to only ring when called by a contact. The downside is that I've missed imp

That's already the de-facto situation on iPhones a lot of the time - you can set it to only ring when called by a contact. The downside is that I've missed important calls with that setting on. I'd love the option to opt into only allowing calls from some kind of verified white-list. Or we could just have an FCC that does it's job.