I think that the Personal Carbon Monoxide Detector is pretty much foolish to tote around, since you can't really avoid breathing in carbon monoxide no matter where you go, and would be better off carrying a gas mask or install an air purifier in your home/office instead. But for those who are extremely mathematical and want readings of the air quality around them at all times can settle for this Personal Carbon Monoxide Detector. This palm-sized device is able to detect carbon monoxide fumes and sound an alarm whenever the gas reaches a dangerous level, with a flashing red LED light thrown in for added effect. It tips the scales at just 2 ounces, making it suitable for travel use. A trio of CR2032 lithium batteries are required to power the Personal Carbon Monoxide Detector, and it retails for $39.85.
Source: Book of Joe