Toggling icon

sensor:
  - platform: template
    sensors:
      toggling_icon_sensor:
        friendly_name: Toggling Icon
        value_template: >
          {% if true %}
            Flash
          {% else %}
            Steady
          {% endif %}
        icon_template: >
          {% elif is_state('sensor.toggling_icon_sensor', 'Flash') %}
            {% if states('counter.heartbeat_counter')|int % 2 == 0 %}
              mdi:recycle
            {% else %}
              mdi:trash-can
            {% endif %}
          {% else %}
            mdi:trash-can
          {% endif %}

counter:
  heartbeat_counter:
    name: Heartbeat Counter
    restore: true
    minimum: 1
    maximum: 9999
    initial: 1
    step: 1

automation:
  - alias: Publish Heartbeat
    trigger:
      - platform: time_pattern
        seconds: '/1'
    action:
      - service: counter.increment
        entity_id: counter.heartbeat_counter

  - alias: Reset Heartbeat
    trigger:
      - platform: template
        value_template: '{{ (states.counter.heartbeat_counter.state|int) >= (states.counter.heartbeat_counter.attributes.maximum|int) }}'
        for: "00:00:01"
    action:
      - service: counter.reset
        entity_id: counter.heartbeat_counter