Basically you want this:
It's nice, but it's not necessary. The extra protection provided by a steel back up can be replicated with paper by simply having two or more back ups in separate geographical locations.
Most of this can easily be disabled with Airplane mode, so it's not that hard, unless you want to permanently remove them.
As I said higher up in this thread, a software airgap will always be inferior to hardware airgap, and it is near impossible for the average person to actually confirm that airplane mode is preventing their phone from transmitting any data.