ibuttons and end user application

[Alvin P. Phillips]

I've been lurking for sometime here, but now I need to ask a question.

I would love to use some sort of public key encryption for communication for
multiple users, but the user interface always seems to be a bit problematic for
the general end user.

In my dreamland, a user could point a browser to a secure web-site and log-in
and work with their messages.  But, in order to secure their private key, I
would like for it to reside on their person, perhaps on an iButton
(http://www.ibutton.com).
The public keys would be stored on the server.

I use these buttons for other purposes at my work, and have one with my gpg
private key stored on it (a DS1996).

This web-app would have to run locally (java perhaps) and be able to communicate
with the ibutton over a serial interface.

Any ideas on if this is possible?  Or do you have any other suggestions on
providing a way for a group of separated users to easily use GPG or the like?

Thanks,

Alvin...