Look into using TeamSpeak. I don't know if it runs on a MAC or not.
Basically what I did, was installed WOL Wake on WAN LAN. Previously, I had registered for a subdomain at DYNDNS.org but never really figured out how to use it. Apparently what you do is login to your router and input your DYNDNS username and password. When your computer turns on (WOL Wake On WAN LAN), it updates your IP address. In the end, when your computer turns on, you'll have both DYNDNS updater running along side with TeamSpeak.
If this works, basically set up your TeamViewer account to it saves your computer information. I can currently access two different computers in my house with TeamViewer.
For Wake on WAN LAN to work, your motherboard has to support being able to be turned on externally through PCI-e. Check your BiOS settings, or whatever it's called in a MAC. I'm a PC user, so I wouldn't know.