> Wifi got a bunch of ambient discovery capabilities a bit back that seems exactly targeted to this stuff. Neighbor Awareness Networking, or WiFi Aware for the trademarked industry packaging there-of. It was built into Android 8. There's also even older wifi-p2p/wifi direct (again, spec vs industry branding for the same thing).

The problem with these is that interop is a nightmare. And interop is exactly what you want to get 99.9% working, otherwise the tech is moot.

Apple, and to an extent Google, can do it thanks to their control of the vertical stack. Open-source... has a harder time about it.