Howto add a package to the live-installer?

[Andreas Sauer <asa@techx.de>]

Hi,

i'am new to debian-live.

I use live-build to build a custom live-cd with a included Installer.
I modified the installer with preseeding and a custom udeb who show up 
in the installation menu, great.

All works very fine, now i want to add a Touch-Screen calibration to the 
Installer, so i need to add the package:
xinput-calibrator_0.7.5+git20140201-1+b2_amd64.deb
to the installer, to execute it by late_command via the preseeding file.

But i cannot find a clean way to do it, my solution is now to copy the 
binary to 'config/includes.installer/usr/bin'.

Is there a more clean,automatic way to add a DEB to the installer?
Maybe a 'config/packages.installer' dir would be great?

Thanks in Advance.

Andreas