Problem with implementing this would be the consoles. Do they even have a sound capture mechanism? I know you can use headsets to talk to others, but that seems to me to part of an independent stream from the game content. So, all the consoles would have to have circuitry that would record your voice, digitize it, send it to the game for comparison to the source files.
A PS2 game did this years ago, so yes, it is indeed possible. Not that I'd like to see it by any means though. Talking to my tv is bad enough when its muttering or raging about lag or idiot team members in online games, let alone talking to my single player game to have it do things.
I tried it out in that PS2 game out of curiosity, never liked it though. It also would be quite problematic for a lot of people too due to varying accents and so forth. The game, by the way, for those curious was SOCOM: US Navy Seals, if I recall the title correctly at least... it was SOCOM at any rate.
I assume the shouts will be just like using magic, only without the need to "equip" them to one of your hands. You select whichever shout you want from a menu/list, then press/hold the shout key/button for the shout to activate, hopefully even if you are in the middle of melee combat or throwing magic fire balls.