The research paradigm for biosensing devices has been focussed to explore flexible sensors. Here, the term “flexible” is indicative of the substrate which has sufficient degree of deformability so that it could be suitably placed at any place. Advances in flexible sensing technologies can be observed by the number of smart products in the market as well as with the number of publications exponentially coming out every year in which diversified development in terms of device operation and performance have been explored. However, as is the case for most new developments, there are several challenges and opportunities which this relatively newfangled field is facing, both in the basic and applied aspects. These challenges and opportunities basically lie in three broad areas, namely design, fabrication, and integration of the developed flexible systems to improve the purpose-oriented sensing capabilities, such as sensing characteristics, functionality, so and so forth. In this chapter, fundamental aspect of various sensing films and associated mechanism has been illustrated. With this article, state-of-the-art work on the promising flexible sensing platforms for biomedical applications is also discussed. © 2018, Springer Nature Singapore Pte Ltd.