Yes, there are Linux drivers for Tobii REX and a Gaze SDK for Linux that should work on all modern Linux distributions, including Ubuntu.
Eye position data is available both through the EyeX SDK and through the Gaze SDK, but there are some important differences, mainly in how much effort the application developer has to put in to get things working. So, even if you don’t have to do low level filtering there are more to take care of when using the Gaze SDK:
EyeX SDK: The EyeX SDK provides a data stream for Eye Position where the eye position data is given per eye, in millimeters, in a 3D coordinate system which has its origin in the middle of the screen, with the x and y axes parallel to the screen plane, and the z axis pointing orthogonally out from the screen plane towards the user. Since this coordinate system gives the eye positions relative to the screen, it is straightforward to use the position data in the application.
Gaze SDK: The application using the Gaze SDK needs to configure an Active Display Area programmatically. This means providing three space coordinates corresponding to the upper left, upper right and lower left corners of a rectangular screen plane. The coordinates has to be given in millimeters in the User Coordinate System (UCS), which has its origin in the mid front of the eye tracker device, with the x and y axes parallel to the front surface plane of the eye tracker, and the z axis pointing orthogonally outwards from the front plane. Please note that the front surface of the eye tracker normally is tilted upwards to point towards the user’s eyes, and that this means that there is an angle between the axes of the UCS and the plane of the Active Display Area. The Eye Position data provided by the Gaze SDK is given in millimeters in UCS coordinates. The application normally have to transform these coordinates to coordinates relative to the Active Display Area before they can be used in the application. The validity of the eye position data also have to be checked by checking validity codes in the data packages.