Regarding EyeX metrics, see this reply:
http://developer.tobii.com/community/forums/topic/eyex-controller-accurary-and-precision-test-report/#post-3075
@ritikajain: Pupil diameter information is not available in EyeX
@Jorge: Using two Tobii devices simultaneously is something we want to support in the future, but not for improving metrics: we want it to be possible to use EyeX on multiple screens simultaneously, having one eye tracker per screen.