I got an answer back about the ability to open master channels:
"That’s a great question. Originally we added the restriction because we didn’t know if apps were being certified. This restriction blocks a dev from creating something like a fake HRM that goes against the ANT+ HRM profile. However, since they are now certified we should be able to remove this restriction."
There hasn't been a decision about whether we'll make this available, but we'll discuss it and should know something soon. :)
I'd like to add my vote for being able to create an ANT+ master channel. My use case is calculating bicycle power from speed on a turbo trainer, and I'd like to broadcast that power as ANT+ so that other head units (even the Edge doing the broadcast, if I'm lucky) can receive that power as if it were a real power meter.
Thanks in advance,
Darren