• Use an MQTT broker (e.g., Mosquitto). Process topics in your own apps or automations.
• Integrate with Node‑RED, OpenHAB, Homey or Domoticz via MQTT nodes/adapters.
• Write data to InfluxDB (via Telegraf or Node‑RED) and visualize in Grafana.
• The ESPHome native API is optional; universal coupling works with mqtt: in the device config.

Subscribe to all topics:

mosquitto_sub -h broker.local -p 8883 -u <user> -P <pass> \
  --cafile /path/ca.crt -t 'waterp1meterkit/#' -v

Publish a test message:

mosquitto_pub -h broker.local -p 8883 -u <user> -P <pass> \
  --cafile /path/ca.crt -t 'waterp1meterkit/cmd/restart' -m '1'

ESPHome base config (MQTT):

mqtt:
  broker: broker.local
  username: !secret mqtt_user
  password: !secret mqtt_pass
  topic_prefix: waterp1meterkit
  discovery: false
# For TLS use the secure broker port (e.g., 8883) and certificates as per ESPHome mqtt docs.

Read current values (GET):

curl -s https://waterp1meterkit.local/api/metrics \
  -H 'Authorization: Bearer <token>'

Trigger an action (POST):

curl -X POST https://waterp1meterkit.local/api/actions/restart \
  -H 'Authorization: Bearer <token>'

ESPHome http_request to your own endpoint:

# Requires a sensor with id: current_liters defined elsewhere
http_request:
  verify_ssl: true
button:
  - platform: template
    name: "Send webhook"
    on_press:
      - http_request.post:
          url: https://nodered.local/webhook/waterp1meterkit
          headers:
            Content-Type: application/json
            Authorization: Bearer <token>
          json:
            device: waterp1meterkit
            liters: !lambda "return id(current_liters).state;"