The interesting thing they kept mentioning was tracking the diver's movements. Thinking about this more since I posted, I could see how doing so could help the accuracy of an inertial tracking system immensely, and also explains why you need to compensate for currents by activating it and swimming at a pace that kept you from moving.Any electronic componentry that currently exists in the consumer does not have the accuracy needed for a device like this, but one day I'm sure it will have..
They claim they already have the system working, and only need to shrink the wrist unit, which is a huge box as shown in the video(s). They also claim a Q4 release date, so we shall see soon if their claims hold up...