One thing I've been playing with is a EEG headset with Oculus Rift. My initial idea is to utilize brain patterns with Oculus content to increase certain emotions.

For example, when one is playing Doom 3, the monsters come out closer and scarier when you are already frightened. Or if you're bored, nothing happens to try to increase suspense.

Of course, this could easily be taken to the adult industry. The same feelings of heightened sexual arousal could be coupled with more intense visual stimulation.