Immersion is something everyone strives for. It's the reason why graphics have moved from Pac-Man to Crysis, why there's the whole 3D movement. It's why games support surround sound and subwoofers. The visual and audio senses are pretty much accounted for in video games, but that still leaves three more for future games to take advantage of.
We've got this one started already. Plastic guitars add "realism" to music games. Various peripherals for the Wii help give that feeling that you really are
fishing/boxing/flipping pancakes (probably. I don't actually own a Wii, so I don't know if these actually help with immersion).
This is a big one. Smell, apparently, is a major factor for things like memories. California Adventures had the whole giant screen/moving chair thing down, but they also added different scents that would appear at various stages, like the smell of oranges. Imagine playing Wii Sports Resort and being able to actually smell the ocean. Or Metal Gear Solid 4 and being able to smell the jungles of South America. Or Gears of War and smell the blood... eh, maybe not. But you get the idea.
Um. Possible application for Cooking Mama games, where a pie you make in the game comes out of the screen. And then you eat it.
My dream is that someday there will be a room where you play video games and all your senses are used. I'm not talking some magical brain scanning thing where you go into the video game. I'm talking, say, Call of Duty: Moderner Warfare 7 and you know there's a giant robot nearby because THE WHOLE ROOM IS SHAKING and you can smell the dust and feel the heat from nearby fires. And then you can pause and a pie comes out of the screen and you eat it.
What are your thoughts? How can game makers increase immersion without sacrificing practicality? Anything from more realistic plastic instruments to a gas mask you wear to smell your opponents' fear in multiplayer games.