You need:
- A light source (the sensor bar, which is a "dumb" device in that it is only powered by the Wii and does not actually report any information back to the Wii.
- A bluetooth adapter for your computer. This is how the Wiimote communicates to the Wii, or to your computer.
- Some sites report the Widcomm bluetooth stack (http://www.broadcom.com/support/bluetooth/update.php) will handle the communication and it's free from Broadcom, but it doesn't do as good a job as the Blue Soleil, and you'll need to make sure your bluetooth adapter uses a broadcom chip. Basically, start with the drivers that came with your bluetooth device, you probably might need anything else for basic functionality. (http://www.howtogeek.com/howto/35470/how-to-use-your-wii-remote-as-a-gyroscopic-mouse/)
- Software to translate the Wiimote input into usable "mouse" commands. Howtogeek suggests GlovePie, but when I tried going to their site just now it reports Serbian hacker (https://www.facebook.com/TripleX.Hack3r/info) has taken over the page. So I'd stay away from that for a while. I'll update when I find another input conversion software tool.
Now, a note. I learned all this by spending 2 minutes searching on Google.
Many people report the lights are the hardest part. To prevent the Wii from "grabbing" the Wiimote signal, just turn it off. But the Wii is powering the sensor bar, and so turning the Wii off means no sensor bar. There are some manuals that instruct how to "convert" the sensor bar to a wall-powered device, so the Wii doesn't need to be on. Understandably, this will void any warranty on the sensor bar, and it'll probably ruin the bar for use with the Wii.
So, connect the bluetooth adapter and install the drivers. Install the Widcomm stack from Broadcom. Connect the Wiimote. Configure the conversion software.