Right, but even key fobs are no better than sending a token to your phone. If this was to really get adopted -- by both the issuer and the user -- it would hav

Right, but even key fobs are no better than sending a token to your phone. If this was to really get adopted -- by both the issuer and the user -- it would have to be easy. A bluetooth device would be ideal, as it would allow wireless communication to the target device being authenticated. Stick it on your keychain and forget about it.