One of the most referred and promising Wireless Sensor Network (WSN) applications is health monitoring. The small size and portability of nodes have made WSNs the perfect tool to easily monitor a person's health condition. In this type application, as well as in several other critical applications, reliability and mobility are paramount. In this paper we propose a method, based on WSNs and mobile intra-body sensors, to accurately detect the fertile period of women on time and other applications based on intra-vaginal temperature monitoring. In addition, our proposal also introduces the proposal of intra-body micro-cameras to monitor the women's cervix, capable to detect related pathologies. To efficiently support this mobile multimedia application, guaranteeing reliability in a continuous monitoring mode, we make use of a new WSN paradigm based on mobility proxies.