Binary Switch/Sensor from Alarm panel state for Homekit?

I’d like to create a binary sensor or switch that is effectively “triggered” or “not triggered”. I want to then use that entity to drive audio announcements via Homekit.

I’ve set up a super basic alarm panel using the manual integration. I suspect I need to use a template sensor, but I can’t figure out the proper formatting.
Here’s what I have so far, but it doesn’t seem to work. I’ve not done much with template sensors other than copy and paste. I tried to find something similar without luck, so this was my attempt. Any help would be appreciated.

  - platform: manual
    code: 1234
    delay_time: 30
    arming_time: 30
    trigger_time: 30
  - platform: template
        friendly_name: "Homekit Alarm Status"
        device_class: motion
        value_template: "{{ is_state('alarm_control_panel.ha_alarm', 'triggered') }}"