[SomeStupidPoint]

It's not totally secure, but why not just a physical button that enables a bluetooth device that transfers a token?

I think you could even have a BT pin, so it would require a little security (eg, neighbors don't have your pin). It should be relatively straightforward to have a BT profile for "token authority".

It certainly would be reasonably easy to use on most devices: just press button and connect to the token device.

[caf]

I think it makes more sense to use the WiFi radio, if for no other reason than adding a BT transceiver to the BOM is probably a nonstarter.