DiverBry:Another thing that hasn't yet caught on in rec diving is underwater wireless communications. In low-viz, if you lost your buddy, you could instantaneously push-to-talk, and let them know you're okay.
There are several problems with wireless coms. First, for the most part, they require the use of a full face mask and that introduces a whole new set of equipment configuration and skill issues.
Second, being able to talk to someone doesn't tell you where they are and if they are in trouble they aren't going to do a lot of conversing. Also most wireless coms a ultrasonic and won't transmit through obstructions. Turbidity in the water of even thermoclines can be a problem.
Hard wire coms with surface support/control of the dive (as done in commercial diving) is a different matter but, IME, untrasonic coms in recreational diving is just an expensive toy that doesn't contribute significantly to safety.