We have a solution to solve communication problems while on a multi-pitch climb or at your local crag! We need your feedback!

Make sure you have a good disclaimer when you sell it to them. If not you are going to get sued when someone hits off belay by mistake and dies.

Other problems to consider - Battery life will be a problem if your LED's are always shining.  Daylight visible LEDs will really suck battery.  How will each operator get a verification that their input or state change was registered not only by their own device but also by the other device and operator.  How would an operator know that their own device sent the "off belay" and the other operator got it?  Waterproof enclosures with LEDs and buttons are a major challenge not to mention sealing the battery access or charging port.  If you are using a standard protocol like bluetooth LE, You will need to indicate to each operator that each device is paired (or not paired) with the other.  And along with the earlier comment about colorblind guys, a great number of older climbers like myself are presbyopic and wont be able to read the tiny lettering that you will try to print on the device unless we bring along reading glasses which isn't an option.  And finally, a device with buttons or LED's clipped to my harness won't survive very long.

Hilarious!  

My calendar must be busted - Is it April Fool's already?

Here in Russia we say "Когда коту делать нечего, он яйца лижет". Which could be more or less accurate translated as "When a tom cat has nothing to do it is licking its balls". Sorry.

I think you're trying to fit a square peg into a round hole - communication is a problem, sure, but the fact that most climbers still don't use commercially available battery-powered communication devices (talkies) should tell you that technology might not be the solution. 

As for the device as you've envisioned it, a twist-select is a good idea vs a button, but it might still get caught up and twist when you don't want it to. And do you need it to communicate more than a binary on belay/off belay?

i have an idea.  just poke a hole in the end of a coffee can, thread the rope, and tie a stopper knot.  do it on both ends and you can just talk back and forth, no problemo.

Looks like the perfect next product for Extare!