I reached out to Vacuum Labs (maker of the Adalite wallet) to see if they wanted to make an air-gapped version of Adalite. Once we have that we can run it on a Raspberry Pi 2b (it does not have built in wifi). I want to see if they are willing to make it and what it will cost and put together a proposal for it’s implementation. In the Ethereum world you can do it with MEW (My Ether Wallet) now. https://www.myetherwallet.com/
Ledger and Trezor are good and useful devices but airgapped functionality is I think an important part of a suite of solutions to meet peoples various needs.
In this post are some links to a device we have been fooling around with to give you some ideas as well as a link to one of 2 videos Charles made on the topic of security:
Air-gapping is probably the gold standard for security. the goal is to make it cheap and easy to implement and use for a wide variety of people.