Hi Gal,
Sorry for late reply. We have done some brief testing to see if this can be accomplished by using the GetThreadExecutionState function on an application level, but not come up with any working solution yet.
I read earlier that Microsoft arranged a hackathon where one of the teams helped Steve Gleason to be able to turn on/off his Surface tablet using his eyes. You probably read this too: http://blogs.microsoft.com/firehose/2014/07/31/oneweek-hackathon-outcome-as-individual-parts-we-were-good-together-we-were-so-much-better/
“For the eye-controlled Surface on/off feature, the team came up with a firmware edit to make it possible.”
Even though Steve does not use exactly the same Tobii eye tracking solution as you, maybe this Microsoft team can share some knowledge about what they had to do to keep the eye tracker running even though the tablet is asleep. That would be in line with their new open strategy.