Thank you for your answer. While eviacam seems interesting,
it looks like you need to be able to move your head to use
it, which unfortunately is already too much for someone in
locked-in sydrome.
I will read references you provided anyway, I'm sure it will
help me to grasp more relevant information on how to integrate
such a heavily constrained requirements into GNOME.
Right now I have to read and make smaller GNOME development
projects in order to better accommodate with the GNOME
devlopment and design. I'm a bit stuck with some compilation
problems in the jhbuild process. So for now I will already begin
with development tools available on my Debian Wheezy box, until
I get rid of my jhbuild tangles.