Send a post request when any of your Mac's cameras are on or off. (https://www.hammerspoon.org/)

hammerspoon.lua

API_URL = 'http://192.168.1.2:8123/api/services/switch/'

function sendCameraStatusToHomeAssistant(inUse)
    print("sending meeting signal: " .. tostring(inUse))
    local endpoint = inUse and 'turn_on' or 'turn_off'
    local fullUrl = API_URL .. endpoint
    local jsonData = '{"entity_id": "switch.your_id"}'

    hs.http.post(fullUrl, jsonData, {
        ['Content-Type'] = 'application/json; charset=utf-8',
        ['Authorization'] = 'Bearer YOUR_TOKEN'
    })
end

function atLeastOneCameraInUse()
  for key, camera in pairs(hs.camera.allCameras()) do
      if camera:isInUse() then
          return true
      end
  end
  return false
end

function cameraPropertyWatcher(camera, _changedProperty, _scope, _element)
  sendCameraStatusToHomeAssistant(atLeastOneCameraInUse())
end

function listenCamera(camera)
  print("listenCamera:" .. camera:name())
  camera:setPropertyWatcherCallback(cameraPropertyWatcher)
  camera:startPropertyWatcher()
end

function cameraWatcher(camera, event)
  if event == 'Added' then
      listenCamera(camera)
  end
end

hs.camera.setWatcherCallback(cameraWatcher)
hs.camera.startWatcher()

for key, val in pairs(hs.camera.allCameras()) do
  listenCamera(val)
end