Hi Steven (@chensteven), The Tobii TX300 will work only with the Tobii Pro Analytics SDK and not with any of the EyeX SDK tools.
Product info for the Analytics SDK can be found @ http://www.tobiipro.com/product-listing/tobii-pro-analytics-sdk/
There is a possibility that you can use the Analytics SDK together with Unity as one of the bindings it supports is C++, however such a setup has not been tested and is not officially supported.