I'm actually working on something based on this idea - I've created a SIM card for the Internet of Things - basically a smartcard (microSD form factor) that offers a persistent crypto-secure identity for Internet-connected objects.

It works by holding the TOR hidden service private key inside a tamper-resistant smartcard and generating/signing hidden service descriptors with it (plus an entire mechanism to prevent you from signing future descriptors - meaning that the identity is closely tied to the physical SIM card, just like in the GSM world - whoever has the SIM has the identity, once you've removed the SIM the identity goes with it).

Discussion at https://lists.torproject.org/pipermail/tor-dev/2016-June/011... - I've made progress since that post, it's now fully operational and tested, just need to figure out a way to turn it into a product and get some funding for it.