I built Lift Tempo Coach for controlled strength sessions where the cadence matters. Configure eccentric, bottom hold, concentric and top hold timing (for example 3-1-1-0), then follow the phase and vibration cues from the watch.
It supports reps, sets and rest, includes four on-watch presets, and reports active time under tension per set and for the full session without counting rest or paused time. The last session summary stays on the watch.
I am the developer. The app is completely free, works offline and sends no data. It guides the timing you configure; it does not detect motion, judge form or replace professional coaching.
Store: apps.garmin.com/.../0487acd8-0c10-4718-b3ae-323f0d8209b3