Well, the inside of the ear is pretty constant temperature regardless of comfort, I believe. Otherwise, those fever thermometers couldn't read in there. How about a ring instead?

Ron

the problem her is far more complex than body temperature, core temperature, and inner ear temperature are relatively constant, the feeling of cold or hot comes from many variables effecting the heat transfer of the body, for instance, fat insulates, so generally a larger person will lose more heat than a thin person, but also, the body must lose as much heat as it produces through its chemical reactions, so a person with a fast metabolism, or a person who has done strenuous activity will produce more heat, and therefore need to lose more heat by having a lower ambient temperature, also, everyone has a different comfort level, so this is truely not as simple as you think, though possible through other methods.