Ok, I was able to figure it out. It looks like other people have tried this before, and were unable to get it to work due to the fact that FreeBSD doesn't allow directed broadcasts. What you need to do is install the ShellCmd package and add a command to add at bootup for a static ARP entry for the machine you want to wake up.
The command is:
arp -s IP Address MAC Address
Then setup a UDP port forward for the WOL packet. The destination IP should be the IP address of the machine you are waking up. The destination port should be the port your WOL client uses.
Thanks to the following sources for helping me figure it out. Hope this helps others.
http://www.neowin.net/forum/topic/966318-wake-on-lan-from-outside-network-remote-via-internet/
http://forum.pfsense.org/index.php?topic=31937.0
http://www.mail-archive.com/support@pfsense.com/msg07379.html