My approach was to buy a bunch of 433Mhz radio-based "alarm buttons" from Aliexpress. Then I could wire up a simple radio-receiver to an ESP8266 device to hand

My approach was to buy a bunch of 433Mhz radio-based "alarm buttons" from Aliexpress. Then I could wire up a simple radio-receiver to an ESP8266 device to handle the presses. Or of course you could use an SDR-receiver on a PC to do something more complex: https://blog.steve.fi/creating_an_iot_button__the_smart_way.html https://blog.steve.fi/creating_an_iot_button__the_smart_way.... https://blog.steve.fi/decoding_433mhz_transmissions_with_software_defined_radio.html https://blog.steve.fi/decoding_433mhz_transmissions_with_sof...