diff --git a/pkgs/development/mobile/androidenv/fetchrepo.sh b/pkgs/development/mobile/androidenv/fetchrepo.sh
index 10c106ff96c5..61f8aa66fe7c 100755
--- a/pkgs/development/mobile/androidenv/fetchrepo.sh
+++ b/pkgs/development/mobile/androidenv/fetchrepo.sh
@@ -8,7 +8,7 @@ die() {
 
 fetch() {
     local url="https://dl.google.com/android/repository/$1"
-    echo "$url -> $2"
+    echo "$url -> $2" >&2
     curl -s "$url" -o "$2" || die "Failed to fetch $url"
 }
 
diff --git a/pkgs/development/mobile/androidenv/mkrepo.rb b/pkgs/development/mobile/androidenv/mkrepo.rb
index bc94ce670f03..a4e3b336e4df 100644
--- a/pkgs/development/mobile/androidenv/mkrepo.rb
+++ b/pkgs/development/mobile/androidenv/mkrepo.rb
@@ -4,6 +4,8 @@ require 'json'
 require 'rubygems'
 require 'nokogiri'
 require 'slop'
+require 'shellwords'
+require 'erb'
 
 # Returns a repo URL for a given package name.
 def repo_url value
@@ -487,17 +489,21 @@ end
 two_years_ago = today - 2 * 365
 
 input = {}
+prev_latest = {}
 begin
-  input_json = (STDIN.tty?) ? "{}" : $stdin.read
+  input_json = (STDIN.tty?) ? "{}" : STDIN.read
   if input_json != nil && !input_json.empty?
-    input =  expire_records(JSON.parse(input_json), two_years_ago)
+    input = expire_records(JSON.parse(input_json), two_years_ago)
+
+    # Just create a new set of latest packages.
+    prev_latest = input['latest'] || {}
+    input['latest'] = {}
   end
 rescue JSON::ParserError => e
-  $stderr.write(e.message)
+  STDERR.write(e.message)
   return
 end
 
-
 fixup_result = fixup(result)
 
 # Regular installation of Android SDK would keep the previously installed packages even if they are not
@@ -505,4 +511,69 @@ fixup_result = fixup(result)
 # therefore the old packages will work as long as the links are working on the Google servers.
 output = merge input, fixup_result
 
-puts JSON.pretty_generate(sort_recursively(output))
+# See if there are any changes in the latest versions.
+cur_latest = output['latest'] || {}
+
+old_versions = []
+new_versions = []
+changes = []
+changed = false
+
+cur_latest.each do |k, v|
+  prev = prev_latest[k]
+  if prev && prev != v
+    old_versions << "#{k}:#{prev}"
+    new_versions << "#{k}:#{v}"
+    changes << "#{k}: #{prev} -> #{v}"
+    changed = true
+  end
+end
+
+# Output metadata for the nixpkgs update script.
+changed_paths = []
+if changed
+  if ENV['UPDATE_NIX_ATTR_PATH']
+    # Instantiate it.
+    test_result = `nix-shell ../../../../default.nix -A #{Shellwords.join [ENV['UPDATE_NIX_ATTR_PATH']]} 2>&1`
+    test_status = $?.exitstatus
+    tests_ran = true
+  else
+    tests_ran = false
+  end
+
+  template = ERB.new(<<-EOF, trim_mode: '<>-')
+androidenv: <%= changes.join('; ') %>
+
+Performed the following automatic androidenv updates:
+
+<% changes.each do |change| %>
+- <%= change -%>
+<% end %>
+
+<% if tests_ran %>
+Tests exited with status: <%= test_status -%>
+
+<% if test_status != 0 %>
+```
+<%= test_result -%>
+```
+<% end %>
+<% end %>
+EOF
+
+  changed_paths << {
+    attrPath: 'androidenv.androidPkgs.androidsdk',
+    oldVersion: old_versions.join('; '),
+    newVersion: new_versions.join('; '),
+    files: [
+      File.realpath('repo.json')
+    ],
+    commitMessage: template.result(binding)
+  }
+end
+
+# nix-update info is on stderr
+STDERR.puts JSON.pretty_generate(changed_paths)
+
+# repo is on stdout
+STDOUT.puts JSON.pretty_generate(sort_recursively(output))
diff --git a/pkgs/development/mobile/androidenv/mkrepo.sh b/pkgs/development/mobile/androidenv/mkrepo.sh
index 81dfdbdb210c..48314f1e9e88 100755
--- a/pkgs/development/mobile/androidenv/mkrepo.sh
+++ b/pkgs/development/mobile/androidenv/mkrepo.sh
@@ -6,7 +6,8 @@ set -e
 pushd "$(dirname "$0")" &>/dev/null || exit 1
 
 echo "Writing repo.json" >&2
-cat ./repo.json | ruby mkrepo.rb \
+pid=$BASHPID
+ruby mkrepo.rb \
     --packages ./xml/repository2-3.xml \
     --images ./xml/android-sys-img2-3.xml \
     --images ./xml/android-tv-sys-img2-3.xml \
@@ -15,7 +16,7 @@ cat ./repo.json | ruby mkrepo.rb \
     --images ./xml/android-automotive-sys-img2-3.xml \
     --images ./xml/google_apis-sys-img2-3.xml \
     --images ./xml/google_apis_playstore-sys-img2-3.xml \
-    --addons ./xml/addon2-3.xml \
+    --addons ./xml/addon2-3.xml <./repo.json 2>/proc/$pid/fd/1 \
          | sponge repo.json
 
 popd &>/dev/null