A quick update on the flow for backups/restores for Google App Engine that I'm building:

1. On your deployment environment, you access an admin-only page where you start the backup.
2. The backup completes and asks you if you want to download it.
3. If you choose to download it, it automatically downloads it to your local machine (your local server has to be running for this to work.)
4. That's it! You can choose to restore it locally and (to be tested) to either your main deployment environment or a secondary (staging) environment on Google App Engine.

Basically, it can be fully-automated (e.g., a "clone deployment" button that does everything you need to populate your local environment with a copy of the data on your deployment machine) and it should Just Work.

The Work in progress: Google App Engine backup/restore flow article by Aral Balkan, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial 2.0 UK: England License.