What the?? Air on or off???

[E. Davis]

Last year when as I was instructing the last checkout dive of an O.W. class at Lake Wazee , I was again reminded of how easy it is to become complacent and simply rely on my dive buddy (or in thes case, a well meaning D. M.) to know their "Righty Tighty from their "Lefty Loosey"when it comes to tank valves and keeping me safe. The students changed out tanks from their first dive, got geared up together, and did their pre-dive checkouts. Great Job, I was thinking to myself! I hadn't bothered changing out my tank as I had plenty of air for the last dive and left my air turned on, less 1/2 turn. I checked out my D. M. buddy, then he checked out my gear as well...he checked my valve, then turned "on" my air for me.... thanks. I took a couple of breaths from the regulator, and got in the water. Needless to say, as soon as I tried to take that third breath, underwater, I had no air! I then realized I had not turned my tank off after the first dive and had allowed my dive buddy to turn OFF my air , thinking he was doing me a favor. Fortunately, we were in the shallows so I only needed to turn my air back on. Yet another lesson learned!
With my story told, and realizing that I must not be the only one that has had this sort of problem with shut or shut less 1/2 turn tank valves, it got me thinking of a way to install a visual indicator on the tank handle, to show at a glance whether the valve is Green for open or Red for shut. Without going into the details of the design, is this something that we, as a dive community would like to see on our valve handles? Wife doesn't want me to spend any more time or money on developing this idea until she's convinced I'm not the only paranoid diver who's been spooked over this situation and thinking he needs one for each of his tanks. Any and all comments would be appreciated. 
Thanks, Ed