I came across a reference to using EvoCam security camera software to read an imput from the audio jack to trigger an event. I can't find any reference to taking this input directly, i.e. without $30 software. I want to use a motion sensor (PIR) to play a file in VLC. Have the script but can't find how to read the trigger - a signal to the audio jack.
Suggestions very welcome!

Found a solution - AudioLeak includes real time monitoring of input, a script reads value and triggers VLC. Unfortunately VLC Scripting commands hard to find. Would like to disable Controls on fullscreen.