Sending Duration in notification

Is it possible to send the ‘duration’ something has been in the current state, via a notification? For example, I send a notification if my garage door has been open for 30 minutes, and I have it repeat that notification every 30 until it is closed. Is there any way I can have the notification send the amount of time it has been open?

Yes, I do this for some stuff in an aquarium (how long the heater was on/off when it changes states, how long the CO2 solenoid has been open/closed when the pH leaves a given range).

Try this:

- service: notify.notify
    message: >
      Garage has been open for {{ relative_time(states.binary_sensor.garage_is_open.last_changed) }}.