I use a 16gb Pro X2 in my 5DIII and my 1DsIII. You can't control the camera remotely.

The 5DIII optimization just means it has a menu list to disable it and show you the status. It will also show a Eye-fi logo on images that were successfully transferred.

I use them to send jpeg previews to my iPad so clients can preview images. I hate being tethered and really hate folks handling the camera looking at the back. This is great when working agencies or shooting heads.