This is a product the world needs.
For decades - since childhood, I think - I've had some sort of chronic sinus problem. Certain things make it flare up, such as a head cold or chili peppers. When it flares up enough, the result is bad breath that could kill a fly at 50 paces. (Which is not even a useful skill in Denver, where we have few flies. Although it does suggest an idea for an offbeat superhero comic.)
Before I got hearing aids, I used to speak too loudly, a common problem with the hard of hearing. Or sometimes too softly, because I feared I was speaking too loudly.
In both these cases, part of the problem is that I can't detect the nastiness myself, so I'm constantly worried that I'm offending other people. What I need, therefore, is an inconspicuous gadget that would warn me. For example, it might be something that would fit on my glasses and flash a signal onto the lenses. Color coded, maybe. A red blink for bad breath and an orange one for speaking too loudly. Something like that.
Other people might need to be warned if their body odor is offensive. The gadget would have to be personalized.
The Offense-O-Meter. I'd pay for something like that.