Home Assistant tricks: manually updated sensor

How to make ANY Entity-based sensor updatable only upon request (standard command_line integration as an example)

If you want to stop HA from updating state of your Entity-based sensor (anything that accepts scan_interval configuration variable) so you can update it when you need by calling homeassistant.update_entity, it's possible using monkey patching and custom integrations.
Note: you should understand that you're playing with HA's internals and your code would break if something changes in HA (class renamed, file structure changed etc). Keep it in mind when designing your setup around this functionality.

You will need to:

1. install the custom integration (manual_command_line in this example) by copying this folder into your <HA configfolder>/custom_components/
2. add the custom integration's domain manual_command_line: to your configuration.yaml (as shown here)
3. declare your sensor as usual

That's it.

To use it with another standard (let's say sensor) integration (template sensor) you need to:

1. rename the custom's integration folder to something unique in HA integrations (my_silent_sensor)
2. in manifest.json set domain to that value (my_silent_sensor)
3. in manifest.json change after_dependencies to your standard integration's domain (sensor)
4. in __init__.py change DOMAIN as per step 2
5. in __init__.py change import homeassistant.components.command_line.sensor to import homeassistant.components.template.sensor
6. in configuration.yaml change manual_command_line: as per step 2 (my_silent_sensor:)
7. declare your standard sensor as usual

sensor:
  - platform: template

8. save changes and restart Home Assistant

If you need to do it with more than one standard integration:

• repeat step 3 adding comma-separated remaining integrations' domains ("[sensor, binary_sensor]")
• add remaining imports similar to the original one
• make sure all as xxx have unique xxx
• use these xxx instead of sensor create as many sensor.CommandSensor.should_poll = should_poll as necessary. Note that you'll need to change class name (CommandSensor) to a class name that your standard integration is based on.