They're kind of a scam. People take a ketone supplement and then urinate on a ketosis strip. The ketosis strip will show that you are in ketosis because you just took in a bunch of ketones lol.
It would be like drinking a bunch of sugar and then doing a fasting blood glucose test. Your glucose levels will come up sky high. Well duh.
Save your money. If you want to get into ketosis, follow a zero carb diet or fast.