Well, maybe. I do now know if this is how it was implemented, but there were plans to have the hall sensor switch for lid up/down resolve as R-Super. The idea being that when the lid closes and the system is set to stay 'on', the shoulder button behavior can be changed/shifted via R-Super to be audio track controls or similar or user defined.
I also have this concept of having a magnet on a key chain or ring to activate the hall monitor switch with the lid open to then enter a R-Super password on the regular keys if someone is paranoid to that level.
This can be done without lid sensor working as R-Super. It just needs a demon monitoring lid state, and if it is closed, use alt/ctrl keys to change tracks or whatever.
About using magnet to trigger lid closed, I guess closing lid may also trigger screenlock or suspend or atleast screen blanking with dpms off, that means pyra may not accept password at all. Though I like both ideas.
Configuring deadbeef at least, it's possible to use modifer keys, but not query the state of a special file or otherwise communicate with a deamon. I can't speak for other media players, as that's the one I settled on using on my Pandora, and I never tried the others beyond checking if they supported different media types and supported seamless track changes.