Since a form of alcohol is made during the break down of ketones, I tested a cheap Chinese breathalyzer to see what would happen. Obviously, I tested when I did not drink any alcohol, because that would confound the test. Anyway, with a carbohydrate meal, it doesn't register anything. After one day or so of no carbs, the breathalyzer registers .01 BAC. After two days, .02 BAC. I have not been able to make it go any higher after multiple days. I don't know if there is a rate limit on the process, or if I am just getting too much protein to develop a lot more ketones even though I am trying to keep that in mind.
I have had some ideas. I have tried MCT oil, but it just put it back up to .02 after work. Patrick Arnold is selling some extremely expensive BHB salts. I suspect I might be able to get a D.U.I. with a dose of those, depending on how well the judge understands biology. There are also those raspberry ketones made popular by Dr. Oz. They are probably not from raspberries; this is a term covering a variety of ketones used in industry to impart a fruity smell to various products, and they are not BHB, but probably related in some way. So, they don't sound like something particularly good, but it might be fun to test against the breathalyzer.
Anyway, even with such a limited range, I suspect a dieter or two might be helped with a breathalyzer. If you can keep it at .02, you are probably losing weight. I can't say that for sure because my scale has died, and I really don't need to lose any weight, so I am not being particularly restrictive in terms of calories.
A breathalyzer that senses acetone rather than alcohol is likely to be the solution. There are two markets for this- ketogenic dieters and diabetics. Test strips for blood testing of ketones are high, and people complain that ketones in your urine isn't a accurate marker. Besides, a hundred count box of Ketostix is about $20. You run out and have to order again, but the breathalyzer will keep going for quite some time.