I think this solves the problem with 2-factor authentication really well. I use 2-factor auth on my Google and Dropbox accounts but it's really frustrating that I have to use the second factor (my phone) and think about another layer of authentication. This means that as long as the second factor is nearby I can login, making it as secure as 2 factor auth but usable as regular username and password authentication. Big kudos to the whole team.