afaik TrackIR is generally synonymous with the branded item where you attach an IR camera to your monitor and little trackers to your head and it tracks your head movement using Infrared light (hence, TrackIR). There are other kits that are similar, but nothing more than prebuilt DIY kits sold as “competitors” to TrackIR (sold by NaturalPoint).
Tobii is completely different. That uses eye tracking technology to slave the games camera view to your eyes (and i can presume it can track depth to some degree but i don’t know). From the light perusing i did into eye tracking, the tech looks very patented and it seems Tobii is the only company to have successfully commercialized the tech for the gaming industry and have more or less cornered the market for this tech in game.
That all said, I googled “Microsoft Flight Simulator Tobii” and found this. Right here on these very forums:
Hope this helps