This paper presents the development and pilot of the Teacher Wellbeing Web-based Application (t*) to capture real-time teacher emotional states and triggers. In Phase 1, the t* was developed from literature as an innovative real-time measure of 11 teacher emotional states and five associated triggers. In Phase 2, the t* was piloted with 11 teachers in Australian high schools. Data were collected prior to and after teaching eight modules about emotion regulation to students. The t* appears to differentiate common teacher emotions and triggers. Student behavior and workload were associated with negative emotional states, while staffroom had a positive effect.