ssh-askpass is a small applet intended for use in conjunction with
OpenSSH. It pops up a window and requests the user input their SSH
passphrase. It is not designed to be executed directly, but to be called
by OpenSSH's ssh-add(1) utility. If no controlling terminal is found (e.g.
ssh-add is called from the .xinitrc as part of the X login process), and
DISPLAY is set, ssh-add will spawn ssh-askpass to request the password.

WWW: http://www.jmknoble.net/software/x11-ssh-askpass/