Automated backup tools for sites on shared web hosts

We have several websites at multiple hosting companies (all shared hosts - some using cPanel, others using Plesk) and we’re looking for a way to backup all files and MySQL databases for each site. We’d like nightly or more frequent backups and prefer that it is completely automated.

My current plan is to store all the backups on an Amazon S3 account or similar. But I’m not sure what tools are out there to accomplish the collection and transfer of the files and databases. It would be nice if there’s a way to do everything through a centralized management system, but that’s not an absolute requirement.

Any help or suggestions would be greatly appreciated!

Have you seen http://www.siteautobackup.com/? They seem one very reasonable option.