Well, now that all three "Next Gen" systems are out, and (I believe) they all use Bluetooth (although the 360 might not), here's something that I think would be neat but you'll never see...
You know those video rocker chairs that you see all over the place? I'd be interested in seeing one of these that connects to the various systems and does a couple of things...
Of course, the different software titles would have to be programmed for this - and thus, you'll never see this actually happen, but...
Picture the Rocker chair with speakers (as a lot of these do now a days), but instead of having a cable lying across the room, the system actually sends the sounds to the chair via bluetooth (like the Wii Remote's speaker, but better quality, of course). Proper speaker placement could make for some really neat sound effects around your head.
Second... there are some of these rocker chairs that have built-in rumble, however, this rumble pretty much sucks because it works with the sound effects and not with the game itself. what if the chair rumbled whenever (and where ever) it was told to (again, via Bluetooth)... Imagine playing Eternal Darkness and having something poking you on your sholder or such... while whispering your name through the speakers....