Totally automatically? I would hate that. I do not want computers controlling my life and removing all decision making. Yes, you will still have to click on a button or two, so bear with it if you can..
iTunes Store: Transferring purchases from your iOS device or iPod to a computer - http://support.apple.com/kb/HT1848 - only purchases from iTunes Store
iOS: How to back up - http://support.apple.com/kb/HT1766
iTunes: About iOS backups - http://support.apple.com/kb/HT4946 - including a list of what is backed up.
How to Restore iPhone From Backup - http://ipod.about.com/od/iphonetroubleshooting/ss/restore-iphone.htm
Maybe you wouldn't want it done automatically. I suppose you could be updating using a public computer in a library. We used to do that before we upgraded from a telephone landline modem for Internet.