How about an audible alarm on your computer that lets you know that your pee valve hose has become disconnected?
LMAO
How about a wireless transmitters to tell you what the air is on all your students.
How about blue tooth down load for your camera and housing so you don't have to open your housing on the boat.
How about a wireless transmitter on your camera housing that gives you depth and air pressure.
How about a inexpensive Powerfull DPV with long battery life.
I like the underwater GPS. I have been contemplating taking a GPS in a pelican box, and tieing it to a spool then sink the time between the GPS, Dive Computer, and my dive camera to map new dive sites.