Seedsigner
Did you know this? I have one, build by myself from scratch.
The key component in SeedSigner is a specific version of the Raspberry Pi Zero single board computer (version 1.3) that does not include WiFi or Bluetooth functionality; the absence of these modules ensures that your private keys never leave the device. Communication with wallet software is accomplished using a two-way QR code exchange process. Information about a proposed transaction is displayed by the wallet software on your computer’s screen, encoded in multiple QR codes, and you scan in the transaction information using SeedSigner’s built-in camera. Information about the proposed transaction is then displayed on the SeedSigner screen. Using cryptographic signatures, SeedSigner then proves that it has the correct private keys to authorize the transaction, and QR codes demonstrating that proof are displayed on SeedSigner’s screen. You then use your computers web-camera to input the QR codes generated by SeedSigner to authorize the