This is an announcement of an open-source detection ruleset called OT Sentinel, designed for Operational Technology (OT) and Industrial Control Systems (ICS) protocols such as Modbus, DNP3, IEC 104, MQTT, and OPC-UA. The ruleset includes 29 detection rules for Wazuh and Sigma platforms, mapped to MITRE ATT&CK for ICS. The project is community-driven, lab-validated for Modbus, and intended as an educational and detection engineering resource rather than a production-ready solution. It aims to fill a gap in open-source OT detection capabilities, providing visibility into OT protocol attacks at the SIEM layer. The author requests community feedback and emphasizes testing in non-production environments before deployment. This is not a vulnerability or exploit but a security tool resource.