We present the concept of pattern-triggered tasks which are released when a particular pattern of events occur. A formal event algebra is used to define complex triggering conditions for these tasks, and the detection of triggering conditions is performed within the system by code generated automatically from these definitions. The implementation of the algebra has many desirable features for resource constrained real-time systems, including bounded and low execution time and memory consumption. Furthermore, we present novel schedulability analysis for our pattern-triggered tasks that leverage on existing analysis for fixed-priority and dynamic-priority scheduling policies.