Android: Want to automatically sync backups from your phone or tablet to Dropbox? Consider using the free utility app DropSpace.
Dropbox already has an Android app so why would you want to use a third-party app that syncs with Dropbox? If you like using Titanium Backup or Tasker you can easily automate your backups by setting up those apps to automatically backup to your SD card, and DropSpace will then automatically sync this file with Dropbox without you having to alter the file folder structure to fit everything within the native Dropbox app. There is also a free plugin for Tasker users that adds DropSpace as an action for a task created within that application.
Setup is simple; select which folders should be kept synced with Dropbox and how often DropSpace should sync. Note that when files are added to your Dropbox account they won't automatically sync to your SD card, but if there's a newer version of a file already on your mobile device you can choose to have that file update to the newer version. This is designed so that your phone won't automatically download large files temporarily placed in Dropbox to share with a friend and so you can delete files on your phone without accidentally deleting them from your Dropbox account. While not for everyone, this app has promise if you are very specific about your device backups and/or are a heavy user of Tasker.