As explained on Just Add Sharks website:
The Nintendo Wii Remote has an optical camera in it that is used to detect up to four points of infrared light. The hardware automatically identifies these points and feeds back XY positions through a bluetooth connection. The cutting laser on a laser cutter is an infrared beam, as it cuts through the surface of the material there is a moment where it is reflected off the material and the Wiimote is able to detect the location of the cut.
“I was trying to think of a way to see the dot of light and send that back to a laptop wirelessly and I remembered the Wiimote already did exactly what I wanted,” Martin of Just Add Sharks told Inverse. “The process took about two evenings, I already had the embedded controller to drive the Z axis on the laser cutter and the laptop stuff was made much easier by Brian Peeks’ managed Wiimote Libraries.”
When I asked him what the most difficult thing was in making an elaborate toy a useful maker tool, he admitted it was his own rusty skills. “The most difficult thing was remembering how to program,” he said. “I’ve had a few months off and the Wiimote libraries use a lot of calls that I wasn’t used to, but there were lots of handy tutorials.” He also said he hasn’t played Wii in quite a long time, but neither has the rest of the world. The last game for the Nintendo Wii, Kirby’s Dream Collection, was released in September 2012.
But maybe now the Nintendo Wii can have a second life in maker circles. According to Martin, this modification could be done by anyone with a laser cutter, some Arduino familiarity, and a working Wii remote. Hope you didn’t break it throwing it at your TV.