I have no idea how I could make that and aubrsync sounds like a working solution.
I have not the smallest idea on how I can update the aufs module in my kernel to the latest version without recompiling everything. or compile anything for that mather from aufs git without getting errors I'm hoping someone who does understand a bit about that would help me out

for the intersted persons, here is the "nowear" initrd.gz
Everyone can try their own scripts and see if they get the sync working
http://dl.dropbox.com/u/15024434/initrd_nowear.gz