In the widespread efforts to round up drunken drivers, more and more motorists are being confronted by a piece of law-enforcement technology called the blood-alcohol tester. Several companies are competing to fill the demand for these devices as police departments equip their officers for tactics like spot-check roadblocks.
The machines have come a long way in speed and accuracy since the days when suspects were asked to blow into a glass vial for a wet chemical test. The latest version of Smith & Wesson's $4,300 Breathalyzer measures the level of alcohol in a suspect's...