I just discovered today a nice, unintended feature of Specto: being notified when you or one of your collaborator changes your google document.
The trick is just to add a web watch and point it to that document’s RSS feed. The drawback to this approach, however, is that it requires you to publish that document. I made a short screencast (demonstration video) of that technical prowess 😉 if you have other tricks and cool stuff that you can do with Specto (or google docs + Specto), let me know.