It seems by the responses that my question wasn't clear enough, so let me try again.
I'm aware of the water mod that brings the radio signal to the control unit while the coil is submerged. That is well-documented. What is not well-documented is a user trying to use an antenna from coil directly to the backphones. This would essentially be the water-mod for the Deus "Lite" version.
So, again, how close would the coax antenna have to be to the backphones for the backphones to pick up the antenna signal from the coil? Does it have to be RIGHT ON the backphones? Or up to the shoulder?
Thanks, everyone,
-Ammo
P.S. I'll pick up Andy's book when it comes out in digital form and I can put it on my phone. I understand from an email he sent me that he's currently working on digital protections.
P.P.S. I emailed XP about the possibility of them replacing the control unit with a smartphone app. It's obvious that the technological base is already there for all smartphones. It's probably only a problem of ensuring they protect their IP. In their email response, they would neither confirm nor deny any future plans in this regard--I'll count that as good news!