When you've got a sweet setup with a projector you're probably doing your best to keep the projection area uncluttered. This clever hack projects infrared dots onto the wall so your Wiimotes work without the Wii IR sensor bar.
If you're unfamiliar with the setup of the Wiimote, the design is simple. Each Wiimote has an infrared-sensitive camera in it—the black box at the end of the Wiimote—and the sensor bar is just two IR LEDs that the Wiimote cameras can focus on. Any source of infrared, appropriately spaced, will work just fine.
At the DIY blog Sprite's Mods they were sick of trying to position their sensor bar with their projector setup. It looked bad, people tripped over the cord, and they wanted a design that would blend in or be outright invisible. Their solution was to design a custom IR LED lamp that would cast two intense circles of IR light onto the wall by the projection screen. The light is invisible to the viewers but works great for the Wiimotes. Check out the full build guide at the link below to see how they created the simple lamp to sit on top of the projector, including photos with an IR-sensitive camera that show how the infrared spotlights cast a Wiimote-friendly pattern on the wall.