The Internet-of-Things designates the interconnection of a variety of communication-enabled physical objects, and IoT-based systems and devices must operate with a deterministic behavior and respect user-defined system goals in any situation. We thus defined hybrid controller synthesis for decentralized and critical IoT-based systems relying on a set of rules to handle situations with asynchronous and synchronous event processing. This framework defines a declarative rule-driven governance mechanism of locally synchronous subsystems enabling the hybrid control of IoT systems with formal guarantees of the satisfaction of system-wide QoS requirements. In order to prove the practicality of our framework, then applied if to a critical medical Internet-of-Things use case, demonstrating its usability for critical IoT applications