A fever monitor would be of limited value for containing measles, since the disease becomes contagious a day or two before symptoms appear.
I have many times explained in this forum exactly how an unvaccinated child is dangerous to other people. For example, a teen might have such a mild case of pertussis that he does not know he is sick. But if he goes to visit someone’s new baby, he can spread the disease to that baby. And it is life-threatening in babies.
Since I have made a continuous effort to educate people on this forum about vaccines, I have seen fewer posts by anti-vaxxers. Every time I respond to anti-vax nonsense, I warn those who post that I watch for that stuff, and I respond. I am passionate about preventing these diseases, and, in some cases, effecting complete eradication. We are on the verge of completely eradicating measles and polio worldwide. That is a great thing!
Good work with educating people! Do you have an education or work in the medical field?