Another good example are the javascript microcontroller boards. Because of the event-loop model of the Js engine, they can simply see there's no code to run and

Another good example are the javascript microcontroller boards. Because of the event-loop model of the Js engine, they can simply see there's no code to run and shift into power saving modes without the dev having to do anything special. example: https://www.espruino.com/Power+Consumption https://www.espruino.com/Power+Consumption