diff --git a/README.md b/README.md
index 841263a..b3084de 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,17 @@ Install both [vim-mode](https://github.com/atom/vim-mode) and ex-mode. Type `:`
 
 ## Extend
 
-See `lib/ex.coffee` to add more commands. Contributions are very welcome!
+Use the service to register commands, from your own package, or straight from `init.coffee`:
+
+```coffee
+# in Atom's init.coffee
+atom.packages.onDidActivatePackage (pack) ->
+  if pack.name == 'ex-mode'
+    Ex = pack.mainModule.provideEx()
+    Ex.registerCommand 'z', -> console.log("Zzzzzz...")
+```
+
+See `lib/ex.coffee` for some examples commands. Contributions are very welcome!
 
 ## Status
 
diff --git a/lib/command.coffee b/lib/command.coffee
index cc85247..851f859 100644
--- a/lib/command.coffee
+++ b/lib/command.coffee
@@ -13,7 +13,7 @@ class Command
     return unless input.characters.length > 0
     [command, args...] = input.characters.split(" ")
 
-    func = (new Ex)[command]
+    func = Ex.singleton()[command]
     if func?
       func(args...)
     else
diff --git a/lib/ex-mode.coffee b/lib/ex-mode.coffee
index 264f2ce..7a548f8 100644
--- a/lib/ex-mode.coffee
+++ b/lib/ex-mode.coffee
@@ -1,5 +1,6 @@
 GlobalExState = require './global-ex-state'
 ExState = require './ex-state'
+Ex = require './ex'
 {Disposable, CompositeDisposable} = require 'event-kit'
 
 module.exports = ExMode =
@@ -26,3 +27,6 @@ module.exports = ExMode =
 
   deactivate: ->
     @disposables.dispose()
+
+  provideEx: ->
+    registerCommand: Ex.registerCommand.bind(Ex)
diff --git a/lib/ex.coffee b/lib/ex.coffee
index 303afa8..4839413 100644
--- a/lib/ex.coffee
+++ b/lib/ex.coffee
@@ -1,6 +1,12 @@
 path = require 'path'
 
 class Ex
+  @singleton: =>
+    @ex ||= new Ex
+
+  @registerCommand: (name, func) =>
+    @singleton()[name] = func
+
   quit: ->
     atom.workspace.getActivePane().destroyActiveItem()
 
diff --git a/package.json b/package.json
index a72812d..623c06c 100644
--- a/package.json
+++ b/package.json
@@ -14,5 +14,13 @@
   "dependencies": {
     "underscore-plus": "1.x",
     "event-kit": "^0.7.2"
+  },
+  "providedServices": {
+    "ex-mode": {
+      "description": "Ex commands",
+      "versions": {
+        "0.20.0": "provideEx"
+      }
+    }
   }
 }