“Immersion” is something companies like to drone on when advertising a new monitor or graphics card, or whatever else.
Basically, “immersion” has come to mean that sensation of being inside a game or movie while playing/watching it.
A certain gamer with some knowledge in electronics and/or gadgetry managed to get closer to that meaning of the word than most everyone else.
Basically, he took and combined a Sony HMZ-T1 head-mounted display, a Kinect sensor and a TrackIR5 head tracking gizmo, among other things.
You probably won't earn points for style if anyone is watching you while playing around Skyrim with this thing on.
Still, at $1,500, it is a good deal compared to actual, “official” simulators that can drain even $650,000 from your bank account. Go here to read exactly what and how the guy did it.