Get a extension mobility logged in users MAC address and remotely log them out

I am looking for a way to query the CUCM to get a logged in user's MAC address, and then remotely log them out.

If anyone could point me in a direction to start, that would be excellent!

Have you looked at the Extension Mobility API? You can use that API to discover what devices a user is logged into, and then use the device information to log out that user.