I would not recommend getting a Wii if you don't have too much room to play it in. It is nearly impossible to function the Wii pointer from a foot away. However, if you generally play the Wii sitting on your bed or whatever takes up the most of your room, you should be fine - although you will miss out on one of the best Wii experiences possible, Wii Sports. You must (MUST) have room for Wii Sports, especially when playing with others. Another game that might require too much room is WarioWare. Every other game I can think of can (and should) be played sitting down, without flailing around.
Theoretically, you could construct your own sensor bar with lights that are closer together that would allow you to function the pointer at a closer distance, but you'd have to look into that yourself (although it potentially requires no construction whatsoever).
EDIT: I actually just did it a second ago. I lit two candles and put them close together so that the flames were about 4" apart, changed the sensor settings in the Wii control menu, and I was very easily navigating the Wii menu from less than one foot away from the candle flames. If you just built one with some old TV remotes or put two small light fixtures next to one another (or just use candles), you could easily accomodate the Wii for a smaller living space.
For a larger living space, pull them farther apart.