Actually, that sounds kind of a good idea to me. Like, have http://my.number/ http://my.number/ return the phone number for identification (though it would nee

Actually, that sounds kind of a good idea to me. Like, have http://my.number/ http://my.number/ return the phone number for identification (though it would need some permission, I don't want every app to have access to it). Make a HTTP POST with some data to http://my.number/validate http://my.number/validate and have it signed by the carrier, validate it against a list of public keys per carrier. Not sure why that wouldn't work today? It could even be a private/reserved IP address routed by all carriers to their auth service. Edit: obviously, it wouldn't work over Wi-Fi without some cooperation at the OS level.