The Internet-of-Things designates the interconnection of a variety of communication-enabled physical objects. IoT 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 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 sub-systems enabling the hybrid control of IoT systems with formal guarantees over the satisfaction of system-wide QoS requirements. In order to prove the practicality of our framework, it was applied to a critical medical Internet-of-Things use case, demonstrating its usability for safety-critical IoT applications.