The library is "simply" a piece of code that talks to a Wiimote that is sending data to a bluetooth receiver. The library will give you all data that the Wiimote is sending (IR, accelerometer's, buttons) in nice easy to access function calls. What is done with that data is in the programmers hands. I do not personally do much programming with the Windows SDK, but if you can write C# (or C++ if you want to write a wrapper around this library) code that can manipulate a the windows mouse, go for it.
But it wont be very good. PC FPS games use an jittering mouse mechanic for looking. The game centers the mouse. The user moves the pointer, the game reads how far away from the center it is, and rotates the players camera in respect to that. Re-centers the mouse, and repeats the next frame.
The Wiimote is not ideal in this case, because there is no way to automaticy "re-center" the IR, unless you strap a machine to the players arm that will physically move it back to the center in less then 1/60th of a second. There are only two good ways to use Wiimote for FPS, the bounding box method seen in Metroid and Red Steel, or good ol' joystick. Since the crosshair in stuck in the center of the screen, bounding box is out, and joysticks are... well... joysticks.
~Quinn