This seems a use case where the smallest the better since the small system only has to close a contact according to a condition on the local network. This could

This seems a use case where the smallest the better since the small system only has to close a contact according to a condition on the local network. This could also be done with a very small uC with Ethernet (example: Arduino and others + w5100 or compatible Ethernet chip; I'm not a fan of WiFi in these contexts). There is also a SSL library that can be used to run a minimal secure web server to host the magic button that would trigger the switch on through the gpio. https://www.arduino.cc/reference/en/libraries/ethernetwebserver_ssl/ https://www.arduino.cc/reference/en/libraries/ethernetwebser... Or it could employ some sort of port knocking on the uC+Eth board so that it wakes up the main system only when the right sequence is used. The advantage of using a uC, lower power draw aside, is that micro SD cards (and their sockets) are less reliable than internal flash.