Hi @leah and thanks for your query. Indeed there has been some movement since the last post!
The X3-120 (which is part of the Tobii Pro Business Unit) does operate with the Tobii Pro SDK which I understand has it’s own Unity Bindings Available.
You can read more @ http://developer.tobiipro.com/unity/unity-getting-started.html
Hopefully this should be what you are looking for! For further information regarding use of this SDK please, reach out to the Tobii Pro Support
directly @ http://www.tobiipro.com/contact/contact-support/ as this forum is principally intended for support with the 4C & EyeX Trackers and their associated SDK’s.