Not something I've had to look for before, as we mostly do this at server level.
However I need a backup solution that will do daily mysql and weekly/monthly files for a resold hosted account running cpanel. I found backomatic.com : Looked promising, but no contact details on site and a privacyguard whois is fishy to me. autositebackup also looked like an opportunity, but part of hostgator which always makes me run a mile.
Any ideas?
Are you looking to backup the entire account, ie, files and databases, or just databases?
I have something in place for my most important sites that emails copies of the database every week, which goes straight to a dedicated Gmail account.
Never had a problem with Hostgator - been with them for years - they've had a few rough patches from expanding too fast, but have felt settled for a long time now.
http://aws.amazon.com/glacier/
JasonD pointed this one out to me, seems to be great value and very fairly priced.
Cpanel has a full account back up feature. You should be able to automate this yourself with cron and some php.