The fifth generation of mobile networks holds the promise to enable new wireless applications, including the operation of dependable and real-time safety-critical systems. However, the strict latency and reliability requirements associated to these systems demand for innovative solutions that enhance the dependability attributes of wireless networks. With this in mind, the adaptation of the bus guardian concept to the wireless context is proposed in this work. This novel mechanism - the medium guardian - is responsible for monitoring and control the operation of a wireless device in the value, time and frequency domains. In this way, failsilent behaviour can be enforced in the nodes of the network by disabling their interfaces whenever a fault is detected.