I watched a video on-line with a guy who used his phone headset as a wired shutter release for his Fuji X cameras.
In my collection of old headsets I found a Nokia with a 2.5mm jack and plugged it into the Fuji's microphone socket .. clicked the microphone button on the Nokia cable and the shutter was released :-)
Have no idea if there are any risks of damaging the camera doing this..