This might surprise you, but the sensor bar for the Nintendo Wii doesn't really sense anything. It actually emits light for the Wii remote's sensors to detect: The sensor bar contains two LEDs that emit invisible infrared light, which the Wiimote uses to fix its position in space, translating that to the onscreen cursor. The long, thin cable tethering the sensor bar to the Wii powers the sensor bar's lights and nothing more--there's no data sent between the sensor bar and the Wii console.
Once the sensor bar's true purpose was demystified, it wasn't long before third-party solutions started popping up. Yes, you can make your own or even fire up a couple of candles. Or you can opt for the Wireless Sensor Bar from Nyko. Instead of the Wii, this sensor bar gets its power from batteries (Nyko claims that the bar can last up to 30 hours on four AA cells, and includes a set of alkaline batteries in the package). The bar can be placed anywhere in the room, and offers much more flexibility for complicated home theaters with large TVs or projectors.
Unlike the original sensor bar, which feels like it could snap in a brisk wind, the Wireless Sensor Bar is an inch-thick, reasonably sturdy piece of plastic. Despite its slightly larger size, the Wireless Sensor Bar can fit almost anywhere the original sensor bar fit, and can even sit securely on the original sensor bar's tiny, clear plastic base. And unlike some so-called wireless solutions we've seen, the Nyko Wireless Sensor Bar is truly wireless.
Since the Wireless Sensor Bar doesn't communicate with the Wii at all, it has no way of knowing when to turn on and off. Obviously the bar can't simply stay on all the time, or else it would go through batteries faster than most Wii remotes. Fortunately, Nyko realized this, and incorporated this knowledge in the sensor bar's controls, which consist of exactly one button and one switch. The button, which rests on the top side of the bar, turns the bar on with a tap and off with a four-second press. The switch, which sits tucked on the back side of the bar, controls the sensor bar's Power Save mode. With the Power Save mode enabled, the sensor bar will stay on for an hour or two (according to the switch's position) before setting off an alarm and eventually turning off. Unfortunately, the bar beeps annoyingly for several minutes before turning off, making it more likely that you'll be getting up and turning the bar off yourself than waiting for it to automatically shut off.
In action, the Wireless Sensor Bar works just like the original sensor bar. You place it above or below your television (or somewhere convenient and in the same direction as the television), and start playing. I plunked the sensor bar on top of my screen, pressed the Power button on my Wii remote, and started playing without any trouble. It's a simple device--just a glorified flashlight, really--and little can go wrong.
If you have a small home theater and keep your Wii right next to your TV, the Nyko Wireless Sensor Bar probably isn't for you. The Wii already comes with a sensor bar that turns on and off automatically and works perfectly well. If you have a more spread-out home theater system, however--with a component rack separated from the TV, or a projector elsewhere in the room--you should consider getting the Wireless Sensor Bar. It makes your Wii setup that much more flexible, and reduces the chances of cord-tripping-related disasters. Unfortunately, it must be turned on and off automatically, and either beeps annoyingly or eats up batteries if you forget about it. Still, if you have a big screen and want to keep cords to a minimum, the Wireless Sensor Bar is a good choice, especially when you factor in its price tag--less than $30.