RHost type authentication is supported by SSH, but I'm not aware of any places that support it.
ATM Card Metaphor: To get access to your funds, you need your ATM card and your PIN. To get access to your account you need a private key file and your passphrase. (Notice the absence of 'like' or 'as' - this is NOT a simile.)
This page will have links to old SSH pages at MSRI.