Zeokat php can perfectly take care of this (albeit only in cli-mode). In a previous job I wrote a script that would create a tar-file of both mysqldump and directory files. This tar would be streamed to an online control panel, which would simply proxy it to whatever location you'd like - dropbox, google drive, ftp whatever. No matter how huge the database or the directory was, it would always work (huge magento shops included). The drawback however was time, the process could take up to one hour for a tar-file of a few GB's ?
Nevertheless this process is quite interesting and I'm hoping to be able to add it at one point to Bazaar/Flagrow. While writing this I already have an idea that might make this work too ?
