I am running arm on GNU/Linux in the context of a user that is neither root nor the user of the tor instance that is monitored. Obviously all available connection resolver fail.
I think it is feasible to get the arm user to be able to write an own connection resolver. This could be achieved by adding a new option in armrc that links to a user provided file that implements the listener. I would solve my problem then by writing one that executes sudo -u my-tor-user netstat -np etc. - with the sudo being a NONPASSWD-command via /etc/sudoers.