So you mean an AIR2 as earlier mentioned...or a second stage integrated to the LPI on your BC.scubajay once bubbled...
What I meant was the air build into the inflator / deflator hose. As opposed to having an octopus. I was just trying to keep it plain and simple.
I am opposed for the simple reason that it would be very hard to control your bouyancy during an ascent while breathing off that regulator.