I'm seeing a bunch of wild and crazy solutions on the net for dealing with the short Wii Sensor Bar cable. I wonder why people are going so crazy with this thing when it is a simple two-conductor wire? If you have even the most basic of soldering skills (or not!), you can pretty easily extend the cable. You just splice in some longer wire, and… oh wait, that's all there is! And if you screw up, you can just order a new Sensor Bar from Nintendo for $10.
Here's what I did to extend the cable. If you decide to do this too, you do it at your own risk. I make no warranties and hold no responsibility if you do something like burn your house down… or worse. Why not just wait a couple of months for some pre-made extension cables to hit the market?
Most any wire will do, but I decided to use a 20ft 4-conductor RJ11 cable. Most folks would call this a "phone cord." Why did I use this? Because I had an extra in the closet.
I snipped the RJ11 connectors (the "phone plugs") off the end of the phone cable, peeled back the jacket, and stripped the insulation from two of the wires. I cut the Wii Sensor cable in two, and stripped the insulation.
A little shrink tube (and that handy cigarette lighter again) can keep the connections safe, even if you do a crummy job like I did. Don't forget to slide the "unshrunk" shrink tube over the cable before you solder.
Voila, I now have a 30ft Wii Sensor cable that works perfectly.