Curious about the Wifi backup features of iTunes, since you brought it up, I set them up for my iPhone and they worked. This was all on a Mac, but I'll bet they're identical for Windows.

I was able to backup my iPhone to my computer over Wifi using iTunes once I set it up. It's just a couple of checkboxes in the "Summary" screen. You just need to turn on the checkbox that says "sync with this iPhone over Wifi". (I also had to reboot the computer and the iPhone to let them find each other, but after that it worked.) The confusion before was due to the fact that, though the checkbox uses the word "Sync", the Wifi setting really applies to both syncs and backups.

Then I performed an actual backup, not a sync, by pressing the actual "Back Up Now" button. (Note that I have iTunes configured so that it doesn't manage/sync the music, videos, and books on the iPhone, those sync features are all turned off.)

It worked, it backed up the iPhone, over Wifi, to the computer. The same screen has a setting which says "Automatically Back Up - This computer", though I haven't let it "sit there" long enough to watch it back up the iPhone automatically. My guess is that if I left iTunes up and running and minimized on the computer, then at some point it will just automatically back up the iPhone over Wifi. I'll report back if I ever see it truly doing that automatically.

Though I would understand if you don't ever want to touch iTunes at all, or don't want to leave it running all the time just for getting backups.

I'm curious about how well you do, in the long term, with third party packages for this. My fear would be that backups won't restore properly if I used a third party tool. For example, if an iOS upgrade happened and the backup was missing something critical that was new in that version of iOS.

A quick final note, if you ever do back up with iTunes, there's a checkbox option for encrypting the backup. You want that turned on, because, if you don't turn it on, then it won't back up secure things like all your saved wifi passwords, forcing you to re-enter all your passwords when you restore the backup to a new phone.