Install shell-mommy (and run it on failed commands)
diff --git a/modules/mommy.nix b/modules/mommy.nix
new file mode 100644
index 0000000..e60eda1
--- /dev/null
+++ b/modules/mommy.nix
@@ -0,0 +1,10 @@
+{ pkgs, mommy, ... }:
+let
+  mommy-script = pkgs.writeScript "mommy" (builtins.readFile "${mommy}/shell-mommy.sh");
+in
+{
+  home.programs.zsh.initExtra = ''
+    source ${mommy-script}
+    precmd() { if (( $? != 0 )); then; mommy false; fi }
+  '';
+}