Last week, Hologram released a new feature called SpaceBridge. This will allow you to create an encrypted, authenticated, inbound tunnel to one of your SIM cards. You can use SpaceBridge to do everything from running a server on cellular or SSH into a device in the field for remote control applications. You can find the main instructions for SpaceBridge here: SpaceBridge Secure Tunneling.
We'll be making improvements over the next few weeks so please let us know what you think!