Pretty sure I saw a couple of party detection devices shown on some netflix airBnb creators show like 8(?) years ago.
(show had a firehouse in DC revamp, then another episode with a california(?) 70's pad with 70s furniture, decor, pool.. definitely the kind of place you may want to party, yet the owners were hesitant to list it if they could not prevent that...
I believe they used a combination of sound dB meters and carbon monoxide detectors to determine approx number of people and how loud they were.
Sounds like this thing is another interesting way to gauge similar activities, which is interesting, but I would shy away from calling it first.
Maybe 'unapproved gathering detection alerts you if too many cell phones are detected on or near your property' - I dunno.