Hi @kouji and thanks for your query.
I am afraid for the time being, we do not have a global shortcut key for enabling/disabling the Tobii Eye Tracking Service, but I have added your voice to the feature request.
There are available certain workarounds to doing this via 3rd party tools like Autohotkey to enable/disable the Tobii Eye Tracking Windows Service but that is not a procedure we can officially recommend. Apologies for the inconvenience.