My Mac app, CloudPull, closely resembles that description. It runs in the background on your Mac, backing up Gmail, Google Contacts, Google Calendar, Google Drive, and Google Reader. It performs backups every hour, and keeps snapshots for 90 days.
Any plans for a Linux port? Seriously, I'd love to pay you, but don't do iAnything (and for much the same reasons that I don't trust Google with much of anything these days.)
You can download CloudPull from: http://www.goldenhillsoftware.com/
CloudPull is free for a single account. For $9.99, you can upgrade to get premium features including support for up to ten Google accounts.
John