External mic

Yep. I've tested Polycom RealPresence Trio and Polycom CX5100, both of which were listed in the last update. There's also an analog audio in port if you want to go that route, however you need to consider echo cancellation if you do so. As long as the Surface Hub can recognize and install the driver for the connected USB device, it should be able to use that as a mic input, which gives you all kinds of options for rooms with existing audio capability.