it is called ReaddleDocs... That App will sync all your MobileMe files. So just navigate to your files from it, then use the open in Pages feature, make your edits, and have Pages save the file to the MobileMe iDisk.
John, thanks for the suggestion, but I don't see how this is any better than copying files to and from iDisk within Pages. Pages already gives you access to your iDisk files within the app. But you still have to tap "Copy to iDisk" and re-upload every time you make changes & select "replace existing document". It's a tedious manual process vs. your changes being synced with iDisk every time you open the app.