I’ve just modified my tassimo coffee machine with a sonoff zigbee… First job was adding another relay to the sonoff. I did that by soldering a trailing lead to the contacts on the back of the sonoff board for the existing relay.
The circled contacts are the ones you want. Then I connected the normally off contacts to the back of the push button in the tassimo screen. I connected the power to the sonoff to the power (after the switch) inside my coffee machine.
Next created a lighting automation that switches the sonoff off when it is switched on - this has the effect of mimicking a button rather than a switch. So now turning on the sonoff in smartthings effectively pushes the start button on the machine. Tucked everything back into the machine. So now I can make a coffee before I get out of bed in the morning.
The sonoff (and additional relay, the little blue thing) sit in the bottom of the coffee machine)
A bit of a fiddly job and requires some electronic and electrical knowledge. The machine still works manually too.