Just to update, pfSense does support pass-through lists for MAC addresses and source or destination IP addresses. Per-user throttling, session durations etc. can also be configured, though a max session length will apply to MAC-whitelisted connections as well.
They (pfSense) don't directly offer an appliance, but do offer commercial support. Recommended hardware vendors are listed, some with pfSense pre-installed, here:
http://www.pfsense.org/index.php?option=com_content&task=view&id=44&...