We're talking about BLE, still? The radio tech that runs in the so called "junk bands" because propagation is so poor?

My watch loses its connection to my phone if I just put it down and walk around my apartment. I'm all for reasonable paranoia, but Bluetooth isn't going to be enabling mass surveillance any time soon. It barely goes through air, let alone walls.

Anyway, whatever. I'm just bouncing around ideas for faster user interfaces. You could always switch it off or set it to be triggered by the presence of particular wifi hotspots, if you don't mind an initial bit of setup.

Back on topic - the debate is interesting, but I think to get this to the stage of being a BIP we'd need at least another wallet to implement it? Then I guess a BIP would be useful regardless of the design issues. The prefix matching still feels flaky to me but it's hard to know if you could really swipe payments out of the air in practice, without actually trying it.