The blue tooth allows the ACJr and Computer to go physically untethered. The desktop/laptop is still needed because the ACJr does not have a built-in Web Server. Wish there was a way around that though.
From what I recall, with the ACSerial2Web software, the majority of the things you can do online with the ACIII you can pretty much do with the ACJr except monitoring ORP, controlling more items, etc. In fact, he offers ACIII apps for ACJr. If you have an IPhone/ITouch, there's an APP for that
It's a very cool "Free" software option, if you don't have any plans to upgrade your controller.