In /etc/init.d open rcS with an editor and search for "/var/etc/init"
That will give you an idea when init is called during boot.
If you are not happy with that another trick is to use your emu startup script and call your script through that
For example if you use CCcam then edit /var/script/CCcam_2.1.2_cam.sh like this
The emu start up script is the last one called during the boot sequence
This is an idea that just popped in to my head... i didnt test it but it should work just fine