Recent developments of embedded wireless technologies, such as low-cost low-power wireless sensor platforms, uncovered big potential for novel applications. Health care and well-being are examples of two applications that can have large impact on society. Medical sensor networks via continuous monitoring of vital health parameters over a long period of time, can enable physicians to make more accurate diagnosis and provide better treatment. Such network allow emergency services to react fast to dangerous patient’s conditions and perhaps save more lives. For such applications to become viable, their design has to consider fail-safe mode of operation, protection of sensitive user data, and especially provide solution for efficient access control. Given the specifics of these applications, in this work we identify communication pattern that will guarantee the most secure way to exchange medical data, propose a standard based security protocol enabling authentication and data protection, and introduce a mechanism for access control—a crucial building block in privacy sensitive applications. To validate our design we implement a prototype on a wireless sensor platform.