The patents themselves aren't enormously illuminating - because they are quite broad. But people with knowledge of the field can dig in and see if there are any hints as to what approaches they're using.
They fall into two categories - a few patents covering mostly the same thing, basically 'hazard detection' in the usage of immersive HMDs.
Meaning, when you are immersed in VR, you may be wearing noise-cancelling headphones, and you obviously cannot see your surroundings. If there is an emergency - like an alarm going off, or an object moving quickly to your head - it would be good to alert you of it, so that patent is talking about ways of doing that, by allowing certain types of noise through, and by unobscuring your vision if there is a hazard in proximity with your head.
The second type patent deals with head motion detection and image stabilisation in a HMD:
The invention recognises that relatively small, higher frequency movements, representing head wobble rather than a definite movement, can lead to a disparity between the amount of compensation applied by the human psycho-visual system and the amount of change in the apparent viewpoint applied by the HMD system. This disparity can lead to visual discomfort.
The invention addresses this by applying a compensation for small higher frequency movements in addition to that applied (in virtual reality type systems) in respect of lower frequency motion components.
Again, it's very broad, it covers everything from digital image processing through to physically moving screens, and modifying optics to pass images differently in order to compensate for certain motions.
It's hard to discern what technology they may actually be pursuing because they name check as much as possible. But a couple of things come up over and over - seemingly two displays, optical lenses (convex or compound), the possibility of a certain level of electrically controllable 'see through' materials/optical see through, optical markers + depth camera for positioning.
Some obligatory patent pictures:
In keeping with previous rumours, these patents list two Evolution Studios staff members as the inventors, who happen to be 3D/stereoscopic/simulation specialists. They were filed in May 2013.