Here comes a long answer for your short question 🙂
There are currently two types of eye trackers and two lines of SDKs supported through the Tobii Developer Zone:
– Tobii EyeX Controller
– Tobii REX
– EyeX SDK
– Gaze SDK
The Gaze SDK is the low-level multi-platform SDK, and the Tobii REX is the accompanying multi-platform eye tracker. These products have been around for about 1 and a half years.
The EyeX line of products is a new line of software and hardware released in 2014, including the EyeX Controller eye tracker, the EyeX Engine runtime environment and EyeX SDKs for C/C++, Unity and .NET.
Since the EyeX products presently only work on Windows, the EyeX Controller only works with Windows based SDKs: the EyeX SDKs and the Gaze SDKs for Windows.
The Tobii REX on the other hand, currently works with all SDKs on all platforms, including the Gaze SDK for Linux.
The number of platforms, operating systems and programming languages supported by EyeX are expected to grow.