The singularity never seemed so close: according to numerous studies and case reports, electronic devices can detect bad breath with more accuracy than you can. Does that mean that we may one day rely on technology to alert us to halitosis? Not necessarily.
In scientific language, the technical term for a device that detects smelly molecules in your breath is a "halimeter." This device uses sensitive instrumentation to measure levels of volatile sulfur compounds (VSCs) in the air. VSCs are given off by odor-causing bacteria in the mouth, so if a halimeter detects them in your exhaled air, you probably have halitosis.
This process is exactly what your nose does, anyway. By parsing the molecules it detects and noting the scent of sulfur-based compounds, your sniffer can detect halitosis reasonably well - that is, assuming you don't have anosmia, or "nose blindness."
While scientists still detect bad breath the old fashioned way - "organoleptically," or with the nose - they are also increasingly using halimeters to ensure that their experiments are rigorous.
This is one reason why studies on the beneficial effects of alcohol-free antimicrobial rinses - like the one published in the delightfully titled journal Electronic Noses and Olfaction 2000 - often fall back on halimeters for confirmation that specialty breath fresheners may alleviate bad breath.