diff --git a/default.nix b/default.nix
index cf9e3cb1fa..608cd1f314 100644
--- a/default.nix
+++ b/default.nix
@@ -20,6 +20,7 @@ in fix (self:
     nix = import ./nix ch;
     web = import ./web ch;
     go = import ./go ch;
+    py = import ./py ch;
 
     version = import ./version.nix ch;
 
diff --git a/py/default.nix b/py/default.nix
new file mode 100644
index 0000000000..6dc76cb549
--- /dev/null
+++ b/py/default.nix
@@ -0,0 +1,7 @@
+# SPDX-FileCopyrightText: 2020 Luke Granger-Brown <depot@lukegb.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+args: {
+  valveindexinstock = import ./valveindexinstock args;
+}
diff --git a/py/valveindexinstock/__main__.py b/py/valveindexinstock/__main__.py
new file mode 100644
index 0000000000..ac6725bdf9
--- /dev/null
+++ b/py/valveindexinstock/__main__.py
@@ -0,0 +1,40 @@
+import time
+
+import requests
+import bs4
+from prometheus_client import start_http_server, Gauge
+
+IN_STOCK = Gauge("valve_index_in_stock", "Valve index in stock?")
+
+
+def fetch_in_stock():
+    resp = requests.get("https://store.steampowered.com/valveindex")
+    resp.raise_for_status()
+
+    soup = bs4.BeautifulSoup(resp.text, 'html.parser')
+    form = soup.find('form', attrs=dict(name='add_to_cart_354231'))
+    if not form:
+        raise Exception("couldn't find add to cart form")
+    price = form.parent.find('div', class_='game_purchase_price')
+    if not price:
+        raise Exception("couldn't find price")
+    green_btn = price.parent.find('span', class_='btn_disabled')
+    if green_btn:
+        return 0
+    return 1
+
+
+def main(argv):
+    if argv:
+        raise Exception("too many arguments")
+
+    IN_STOCK.set_function(fetch_in_stock)
+    start_http_server(9998)
+    while True:
+        time.sleep(1000)
+
+
+if __name__ == "__main__":
+    import sys
+
+    main(sys.argv[1:])
diff --git a/py/valveindexinstock/default.nix b/py/valveindexinstock/default.nix
new file mode 100644
index 0000000000..f44bc3371e
--- /dev/null
+++ b/py/valveindexinstock/default.nix
@@ -0,0 +1,43 @@
+# SPDX-FileCopyrightText: 2020 Luke Granger-Brown <depot@lukegb.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+{ depot, pkgs, ... }:
+
+let
+  python = pkgs.python3.withPackages (ps: with ps; [
+    requests
+    beautifulsoup4
+    prometheus_client
+  ]);
+
+  filterSourcePred = (path: type: type != "directory" || (
+      baseNameOf path != "__pycache__" &&
+      baseNameOf path != "node_modules" &&
+      true));
+in
+pkgs.stdenvNoCC.mkDerivation rec {
+  name = "valveindexinstock";
+
+  src = builtins.filterSource filterSourcePred ./.;
+
+  buildInputs = with pkgs; [ makeWrapper ];
+  propagatedBuildInputs = [ python ];
+
+  installPhase = ''
+    sitepkgdir="$out/lib/${python.libPrefix}/site-packages"
+    pkgdir="$sitepkgdir/valveindexinstock"
+    mkdir -p $pkgdir
+    cp -R \
+      *.py \
+      $pkgdir
+
+    mkdir "$out/bin"
+    makeWrapper "${python}/bin/python" "$out/bin/valveindexinstock" \
+      --add-flags "-m" \
+      --add-flags "valveindexinstock" \
+      --suffix PYTHONPATH : "$sitepkgdir"
+  '';
+
+  passthru.pythonEnv = python;
+}
diff --git a/py/valveindexinstock/shell.nix b/py/valveindexinstock/shell.nix
new file mode 100644
index 0000000000..d5c5bbe055
--- /dev/null
+++ b/py/valveindexinstock/shell.nix
@@ -0,0 +1,12 @@
+{ depot ? import <depot> {} }:
+
+let 
+  inherit (depot.py) valveindexinstock;
+  inherit (depot) pkgs;
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    valveindexinstock.pythonEnv
+
+    black
+  ];
+}