Breathalyzers tell you how much fat you are burning off during workouts.
Made by British scientists, these gadgets will be able to tell you the moment when a sweaty session on the treadmill finally starts to pay off by detecting when the body has used up its supply of food energy and switches to breaking down fat instead.
Exercise machines estimate when gym rats go into the "fat burning zone".
This (DUI-like) breathalyzer operates via picking up minute changes in the levels of a molecule called acetone in people's breath, which is given off when the body starts to burn fat.
Professor Gus Hancock, a chemist at Oxford University who has set up a company, Oxford Medical Diagnostics, to develop the machine: "Acetone is a molecule that is produced by people who are burning fat rather than food.
"This is of great interest in sport studies and dietary studies to find out how people have worked out in the gym. That is an area we are trying to explore and we are trying to produce a monitor of how well you have burned off some body fat."
California DUI lawyers are interested in this invention.