I want interaction-free TFA in my phone. I want to be able to walk up to a computer, put in my username and maybe a PIN, and subsequently have every website log me in because the browser knows my phone is on the same LAN as the browser or is in NFC or Bluetooth range.

But I would especially want this if the TFA is running on a separate system from the main CPU in my smartphone, only sharing radio/networking hardware at most. This wouldn't be foolproof, but if my smartphone OS company can patch security holes in a timely manner and deliver the patches on-air, then this is good enough for me.

If Authy can deliver the 2nd factor automatically from my iPhone to my other devices through Bonjour, I will rave favorably about them to everyone who will listen.