This seems like the germ of an idea that has many possibilities beyond matching couples. Of course the military and gangs use all sorts of symbolism to identify each other but the conscious elaboration of visual communication has all sorts of private and commercial possibilities.

it seems to me that this idea was suggested before, but I couldn't find it. Are old ideas being deleted from this site?

I think an engagement ring or a wedding ring serves the same purpose as this bracelet you seek, except for the seeking and one-night-stands parts.

I don't believe a O-N-S is a very good idea anyway.

My brother told me when he went to South Padre many years ago, there were girls that would wear a condom on a string around their neck. I guess it was obvious what they were expecting...