Linux mobile wallet
A transaction signer for Substrate chains built on mobile-nixos: an old phone as an offline signing device, declared like any other NixOS system.
An experiment from the same line of thinking as Mind the Gap: a phone that never goes online, running a NixOS image built with mobile-nixos, signing transactions for Polkadot-family chains and handing them back as QR codes. Declaring the whole device in Nix means the image can be rebuilt from source years later, which is the point of a signing device you have to trust.
The project reached a working prototype in 2021 and is kept as a reference; the hardware-key approach of Mind the Gap took over from it.