An RTD or thermistor will do a good job of measuring the temperature of whichever surface it is in contact with. If that surface is the skin on a human's body, then that temperature will be accurately reported (within the accuracy and linearity limitations of the sensor, of course). If skin temperature is what you want to measure in your body sensor network, then your solution is very simple. However, if you're attempting to measure the internal/core temperature of the human body, then that becomes more complex.
you can read this to help you with what you are looking for. "Body Temperature Variability (Part 1): A Review of the History of Body Temperature and its Variability Due to Site Selection, Biological Rhythms, Fitness, and Aging.("")":http://www.altmedrev.com/publications/11/4/278.pdf
