Rough instructions, sorry about that.
On a NixOs machine
git clone https://github.com/amaumene/nixos-crying-detector.git
cd nixos-crying-detector
nix-shell -p nixos-generators
Edit all the "your_..." on configuration.nix:
your_wifi_ssid = { psk = "your_wifi_psk"; };
services.colin-crying-detector.api-key = "your_pushover_api_key";
services.colin-crying-detector.user-key = "your_pushover_user_key";
openssh.authorizedKeys.keys = [ "your_ssh_key" ];
initialHashedPassword = "your_hashed_password";
Generate the img and copy it to your SD card
nixos-generate -f sd-aarch64-installer -c configuration.nix