[vbox-dev] Custom gui frontend: custom ExtPack or other means of direct host/guest com?

[aep]

greetings,

is there any documentation about building extension packs?

The reason i'm asking is that i require to transfer the screen to a 
different gui frontend, but the available means are all insufficient.
Getting the framebuffer pointer requires rebuilding all of virtualbox 
(as the security implementation won't let you run your own frontend by 
default)
Transfer over UDP doesn't work as udp networking is still unstable as 
of vbox 4.1.4.

So my next attempt would be to write a custom pci device and add it as 
extension pack, but for that i cannot find documentation.

Thanks!