I know the Wii is more interactive than most games, but some guy at Carnegie Mellon University in America is taking it all a couple of steps further.
It all seems like fairly simple steps, since the whole system is based on calculating the position of an LED using a sensor, but when he includes things like head tracking so that single-player games could have one Wiimote to shoot/fight with and one set of sporty shades with LEDs to change your view then it gets to interesting levels of interaction.
If/when they actually release something like that then all those times you spent trying to lean around the corner to see what there was in a FPS game or leaned into a corner in a racing game might actually begin making a difference!
Carnegie Mellon play with Wii consoles