With WP Client Reports Pro, you can add a new section to your report that gives you and your client statistics about the backups of their website. The plugin looks at the stored backups and the dates they happened in order to gather the report data.
BackupBuddy is a premium plugin that allows you to back up your entire WordPress website including WordPress, Plugins, Themes, and Data. You can keep it on your server ship it off to another server for safe keeping.
There is no set up needed once you have the plugin installed.