Saw this one recently -
https://www.youtube.com/embed/jHscTRpz5WQ?feature=oembed
PC in a backpack, OR headset, gun controller and positional tracking like PS move.
Remember Quazar/Laser tag games? If they get the system above right, it could be the equivalent 'arena' gaming of the future.
Imagine a bare warehouse, with a grid of the positional tracking cameras suspended from the ceiling, safety padding on the walls.
You could have amazing multiplayer games played safely - you could see each other in-game very accurately.
You could have almost any kind of team game - say soccer for example, you'd appear to be in a packed arena (there could be actual observers online!) and the opposing team could even be in another similar setup, playing against you online.
A sort of force-feedback 'thumper' on the shoes could simulate ball contact.
Likewise Tennis, golf, you name it.
If the same setting had a set of temporary soft barriers they could erect, you could form a series of walls that match a game map's layout, and have Counterstrike games... for 'real'..