Setting up a remote BOINC client seems to be a bit confusing, mainly due to the lack of error messages. This is what you have to do to get it working.

1. sudo apt-get install boinc-client
2. Modify /etc/boinc-client/remote_hosts.cfg to add the manager's IP address. Do note that wildcards / CIDR ranges don't seem to work!
3. Modify /etc/default/boinc-client to enable RPC control.

Note that if you want to remove hosts from BOINC Manager's interface, you will have to manually edit ${HOME}/.BOINC Manager.