Virtual reality first started being used for pilot training since it is rather dangerous to let beginers have a go on real planes. There are two techniques, haptics and immersion. Haptics in a flight simulator are the mechanical systems that make the mock up cabin move up down left right as if in real flight. For sex vr the haptics can be vibrators that throb in time with the action, or perhaps a cock suck attachment that is synced to a video. Vr sex toys are a tiny part of the market, its an expensive hobby for a small number of fanatics.
By immersion I mean sound and video that immerses your senses. In a flight simulator you'd be wearing headphones anyway so thats the sound part. The video will be seen through the cabin windows so it will be a giant screen. For me headphones are the only way to hear porn, the sound has to be inside your head, blocking out the outside world. What matters for the video part is that the image fills your view so there is no connection to the real world any more. You can do that with a normal screen if you can fix it right up close to your face. Its more comfortable, less eye strain, to use a dedicated headset if you have money to spend. Then there are the 3D films which add an extra level of realism but there arent many to choose from. Finaly whats hot at the moment is the 360 degree system, where you turn your head to the left and the image turns to the left too. Or to the right or up or down. Could be very hot for an orgy scene, for one on one sex there is less extra detail I suppose. Problem again is not much good porn available in the new format so its not worth spending much money on. A Google Cardboard is a very cheap way to experiment with the effect so youve lost little if you dont like it. Good headphones are worth paying for, they really make a difference.