There is a hand-made replacement for pkexec and the good old gksu
and gksudo:

In your sudoers file (edited with visudo), put the following line

Defaults env_keep = "XAUTHORITY DISPLAY"

Note there can be other variables in the list, like EDITOR, but the
above are the ones which will allow you to run GUIs under root priviledge.

Then allow yourself to run foo with sudo (also by editing your sudoers
file vith visudo) and then

sudo foo

hth

--     Didier