KDE / ksshaskpass

Ksshaskpass is a front-end for ssh-add which stores the password of the
sh key in KWallet.
Ksshaskpass is not meant to be executed directly, you need to tell
ssh-add about it. ssh-add will then call it if it is not associated
to a terminal.
From the ssh-add manpage:
/----------------
|  DISPLAY and SSH_ASKPASS
|    If ssh-add needs a passphrase, it will read the passphrase from the
|     current terminal if it was run from a terminal.  If ssh-add does not
|     have a terminal associated with it but DISPLAY and SSH_ASKPASS are
|     set, it will execute the program specified by SSH_ASKPASS and open
|     an X11 window to read the passphrase. This is particularly useful
|     when calling ssh-add from a .xsession or related script.  (Note that
|     on some machines it may be necessary to redirect the input from
|     /dev/null to make this work.)
\----------------

This means you need to make sure to set the SSH_ASKPASS environment variable
to the path of ksshaskpass and then call ssh-add from your autostart scripts.

To add it to the KDE autostart sequence you could for example create an
executable script with the following content in ~/.kde/Autostart/ (or maybe
/.kde4/Autostart/, depending on the distribution).

/----------------
|#!/bin/sh
|
|SSH_ASKPASS=ksshaskpass ssh-add < /dev/null
\----------------