I admit that besides reading some of the documentation (several hours, actually) I have not tested a fully functional system (installed/deinstalled within a few days), so I might not have all the details.
However, I understand that a cell phone is used in two ways. First, as a remote controller. I believe that at this moment this function is limited to Symbian phones - for which there are very few models in America. They are supposed to be working in other models.
The second and most creative use is the one that you mention. It uses the cell phone's Bluetooth to work as an RFID. By pairing the bluetooth phone to the closest PC in the house it detects were each person of the house is located. This can trigger any type of action, as you say. But the most unique one - and the one that they demo in their flash presentation is multimedia.
Actually, I wonder if it really needs a cell phone.. After all, it works just by pairing bluetooth devices. Probably any other bluetooth device serves the same purpose without requiring the cell phone part. Once bluetooth earphones get small enough it would be possible to achieve the same results just by carrying a little earphone inside your ear canal. And then you would be able to receive private messages from your house directly to the bluetooth earphone. You could even dial a call from anyplace in your house or send any VR command by speaking to your HA system via your earphone. Several orders of magnitude cheaper than a full house echo-cancellation voice recognition system.
