I sometimes consider a pony bottle, but rarely see them used by recreational divers. I wouldn't want it to be a reason to become cavalier about monitoring my console (and I don't think it would).
What are the other considerations that keep people from using them (and conversely, those that choose to carry them)? Is it just cost that's a hurdle?
What are the other considerations that keep people from using them (and conversely, those that choose to carry them)? Is it just cost that's a hurdle?