  Continuous health monitoring using wireless body area networks (WBANs) of
wearable, epidermal and implantable medical devices is envisioned as a
transformative approach to healthcare. Rapid advances in biomedical sensors,
low-power electronics, and wireless communications have brought this vision to
the verge of reality. However, key challenges still remain to be addressed.
This paper surveys the current state-of-the-art in the area of wireless sensors
for medical applications. Specifically, it focuses on presenting the recent
advancements in wearable, epidermal and implantable technologies, and discusses
reported ways of powering up such sensors. Furthermore, this paper addresses
the challenges that exist in the various Open Systems Interconnection (OSI)
layers and illustrates future research areas concerning the utilization of
wireless sensors in healthcare applications.
