diff --git a/tools/apk_masseur.py b/tools/apk_masseur.py
new file mode 100755
index 0000000..6013e6f
--- /dev/null
+++ b/tools/apk_masseur.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python
+# Copyright (c) 2017, the R8 project authors. Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+import apk_utils
+import glob
+import optparse
+import os
+import shutil
+import subprocess
+import sys
+import utils
+
+USAGE = 'usage: %prog [options] <apk>'
+
+def parse_options():
+  parser = optparse.OptionParser(usage=USAGE)
+  parser.add_option('--dex',
+                    help='directory with dex files to use instead of those in the apk',
+                    default=None)
+  parser.add_option('--out',
+                    help='output file (default ./$(basename <apk>))',
+                    default=None)
+  parser.add_option('--keystore',
+                    help='keystore file (default ~/.android/app.keystore)',
+                    default=None)
+  parser.add_option('--install',
+                    help='install the generated apk with adb options -t -r -d',
+                    default=False,
+                    action='store_true')
+  parser.add_option('--adb-options',
+                    help='additional adb options when running adb',
+                    default=None)
+  (options, args) = parser.parse_args()
+  if len(args) != 1:
+    parser.error('Expected <apk> argument, got: ' + ' '.join(args))
+  apk = args[0]
+  return (options, apk)
+
+def findKeystore():
+  return os.path.join(os.getenv('HOME'), '.android', 'app.keystore')
+
+def repack(processed_out, original_apk, temp):
+  processed_apk = os.path.join(temp, 'processed.apk')
+  shutil.copyfile(original_apk, processed_apk)
+  if not processed_out:
+    print 'Using original APK as is'
+    return processed_apk
+  print 'Repacking APK with dex files from', processed_apk
+  with utils.ChangedWorkingDirectory(temp):
+    cmd = ['zip', '-d', 'processed.apk', '*.dex']
+    utils.PrintCmd(cmd)
+    subprocess.check_call(cmd)
+  if processed_out.endswith('.zip') or processed_out.endswith('.jar'):
+    cmd = ['unzip', processed_out, '-d', temp]
+    utils.PrintCmd(cmd)
+    subprocess.check_call(cmd)
+    processed_out = temp
+  with utils.ChangedWorkingDirectory(processed_out):
+    dex = glob.glob('*.dex')
+    cmd = ['zip', '-u', '-9', processed_apk] + dex
+    utils.PrintCmd(cmd)
+    subprocess.check_call(cmd)
+  return processed_apk
+
+def sign(unsigned_apk, keystore, temp):
+  signed_apk = os.path.join(temp, 'unaligned.apk')
+  apk_utils.sign(unsigned_apk, signed_apk, keystore)
+  return signed_apk
+
+def align(signed_apk, temp):
+  print 'Aligning'
+  aligned_apk = os.path.join(temp, 'aligned.apk')
+  cmd = ['zipalign', '-f', '4', signed_apk, aligned_apk]
+  print ' '.join(cmd)
+  subprocess.check_call(cmd)
+  return signed_apk
+
+def masseur(
+    apk, dex=None, out=None, adb_options=None, keystore=None, install=False):
+  if not out:
+    out = os.path.basename(apk)
+  if not keystore:
+    keystore = findKeystore()
+  with utils.TempDir() as temp:
+    processed_apk = None
+    if dex:
+      processed_apk = repack(dex, apk, temp)
+    else:
+      print 'Signing original APK without modifying dex files'
+      processed_apk = os.path.join(temp, 'processed.apk')
+      shutil.copyfile(apk, processed_apk)
+    signed_apk = sign(processed_apk, keystore, temp)
+    aligned_apk = align(signed_apk, temp)
+    print 'Writing result to', out
+    shutil.copyfile(aligned_apk, out)
+    adb_cmd = ['adb']
+    if adb_options:
+      adb_cmd.extend(
+          [option for option in adb_options.split(' ') if option])
+    if install:
+      adb_cmd.extend(['install', '-t', '-r', '-d', out]);
+      utils.PrintCmd(adb_cmd)
+      subprocess.check_call(adb_cmd)
+
+def main():
+  (options, apk) = parse_options()
+  masseur(apk, **vars(options))
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(main())