I would love to see an ssh-like key exchange built into browsers. You add your key to the site, GitHub style, and then you use that for auth. No more nonsense with OAuth or "remember my password" or the remote site having your password just because they grabbed the DB. It's just a useless public key to them.
SSL Client certificate authentication has existed in browsers for a long time. Browsers even have built in key generation, but noone uses it. Probably because the UI is not very good.
Mozillas new BrowserID scheme is pretty similar to this too.
PKI as implemented by SSL Certs is needlessly complicated, which is a big part of why no one has adopted it for end user authentication. Compare what I described above to the mess described here: http://en.wikipedia.org/wiki/Public-key_infrastructure
A decentralized key system as ssh provides is much more appropriate for end users.
In fact, I can't think of any VPN I've ever connected to that didn't require a machine certificate. Cisco VPNs I've used require it, as does my own personal VPN.
