Triggering an action on a Pi when the button is pressed

I'm trying to figure out the same thing. See this comment for my thoughts on how it might be solved. I'm sure Gordon will be here soon with a helpful answer, as always :)

If you're comfortable with Node, you might try using noble and Espruino's UART service over BLE like I did (node code, espruino code). Though, as Gordon pointed out, a continuous BLE connection uses much more power, so I'm looking for a better solution.