Wireless Body Area Network (WBAN) applications help reduce medical costs and improve people's quality of life by monitoring a user's biological signals via wearable and implantable wireless sensors. In order to satisfy burgeoning requirements, context-aware solutions are needed, thus allowing the system to adapt to changes in the user's mood, mental states, biological signals, and the environment. Thus, contextual information must be measured alongside biological signals in order to characterize and understand the current situation to adapt the system. With these issues in mind, this survey presents an overview of context-aware solutions at the Medium Access Control (MAC) and application layers. A clear distinction between medical and non-medical applications is made and some promising latest commercial WBAN products are highlighted. We show that, despite the importance of context-awareness in WBAN applications, there are limited solutions available, particularly at the MAC layer. The survey concludes with a discussion on open research challenges for future context-aware WBANs.