It would be beyond stupid for a healthy "diet focused" person to want to use this. They're not at risk for ketoacidosis, and there is zero evidence that continually measuring ketones would be useful in any sense. That's different from the purported use of CGMs, which is to monitor for glucose spikes in response to specific foods (and even then, the evidence that monitoring glucose spikes in healthy people has any benefits is really thin).

If someone really wanted to measure their ketone levels there are simple urine tests that do it - there is no need to measure it continuously for healthy people. And if they want to see if they're in ketosis it's pretty easy to determine - if they're on an ultra low carb diet and their breath smells like shit, it's a good sign they're in ketosis.