Wired headphones plugged in as constraint?

[systema-encephale]

I have mapped one button for audio playback control, but sometimes it gets pressed accidentally and then I get loud music in inappropriate situations. So I added a constraint to ensure it only works when my Bluetooth earphones are connected.

That works in principle, but my phone still has a traditional headphone jack and I actually prefer to use my wired headphones, so I would like to use their presence as a constraint. I don't think that option exists, though, or am I missing something? Would it be possible to add this?

(Some apps are able to detect whether headphones are plugged in, so there seems to be some OS level awareness of this.)