In recent years, there has been significant progress in a number of sensing technologies related to on-body measurements, such as platforms for monitoring respiration, heart rate, location and movement. In these cases, these are based on highly effective transducers that are increasingly integrated into garments such that they are becoming innocuous to the user. In contrast, the area of on-body chemical sensing remains highly under-developed. In this paper, I will address the significant challenges that are inhibiting the practical realisation of reliable chemical sensors and biosensors capable of generating accurate data in real time. I will also discuss the central role that materials science (and particularly the trend towards more biomimetic platforms) can play in overcoming these challenges, and present some idea and concepts that could point the way forward.