lowyhong: I don't know if changing the sensor position helps. I want to be able to target something on the screen as I see it, not according to the position of the IR on my Wiimote relative to the sensor. Unless I missed it, there doesn't seem to be an option on the Wii Menu to show this :(
OmegaX: It is as you say, when you point at the screen with your Wiimote you aren't actually pointing at a specific point in space. What really happens is that the Wiimote calculates the angle from the tip of the Wiimote from the center of the sensor bar and transforms this angle to a point in your screen using both edges of the sensor bar as reference.
If you can notice the difference is because your screen is too big compared to the sensor bar. Positioning yourself farther away from the screen should help a little. I've also heard that some people duct tape together 2 sensor bars and cover the middle part of the "longer" sensor bar.
Edit: I don't recommend the "two sensors option" because that would require a second power source (another Wii) or splicing a wire to the second one. You could, however, take one sensor and break one half of the lights off (carefully, cutting the plastic accurately and then spinning the wire on one side) and the splice them back together with wire in the amount you wish to set the sensors apart.
Yeah, there's a number of homebrew 'solutions' because all you need is a source of IR. I've heard ideas of candles and the-like, but I don't know how practical that would be for you. The extended range sensor likely works on the same principle, it's just varying positions of IR lights set into a plastic module. Unfortunately it's not like old Gun-con games which were set according the the display's light patterns, because that required CRT televisions, which a Wii owner obviously can't rely on anymore.
There may be options for 'above' or 'below' the TV, I'll check it out with MP:T and RS2.
Edit: Yes, the "above" and "below TV" settings are in the main Wii settings.
Unfortunately, there aren't the settings you wished for in either of those games
I did some casual preliminary testing to figure out where the pointer felt accurate. On my 32-inch 4:3 CRT with a standard IR emitter, the sensor on top of the monitor (separated by two inches of border), and the Wii settings set to "Above TV" the Wii remote felt accurate at four feet away. Further than that and I had to point slightly outwards to get the same effect.
I assume this means with a wider spread between the IR emitters that you would have to point inwards at four feet and at a longer distance away it would feel accurate.
Also, if I carry the results of my test over, you could set up the standard IR emitter on "Below TV" settings and then place it on a coffee table or something, facing you at a distance of four feet from your assumed stationary position(assuming the same television dimensions) and that may have potential to feel accurate.