I own a Rancilio S24 for a few years and I'm satisfied with it. However, I would really love to install some type of device or switch capable of stopping the extraction after a number of seconds or volume without having the need to manually touch the switch to stop the extraction. Is there such a device? Thank you in advance for any suggestion.

If a BT scale could connect to something like IFTTT it could power off the machine from a smart plug when it reaches the desired weight.

Thanks for the suggestion. I never thought of that. But I was thinking on something more conventional. Don't most espresso machines out there work that way? I mean, the barista press a bottom and let it brew and the machine stops on its own?

Some commercial machines have timers or volume meters. Timers are reasonably common on inexpensive, home machines. Volumetric stop is reasonably rare on home machines. Mid-range home units are often completely manual.

If you have the electrical skills, you could rig up and wire something in behind the existing switch.

I consider shot time as an output, with coffee, grind, dose, and target ratio as the primary inputs.

Thanks for the suggestion. Perhaps a timer relay will do the job. You are right about the time being an output but there are times, when I'm making several drinks back to back, I wish I could grind for the next shot or steam milk, and pull shots at the same time without worrying about stoping the extraction.