"Night vision" is predicated on the idea that infrared light bounces off of objects the same way that any other kind of light does, only that our eyes can't see IR light. So while a room could potentially be brightly lit with an infrared light source, you would see only darkness. Fortunately, camera CCDs aren't human eyes and many are as sensitive to IR light as they are to the visible spectrum. So, ostensibly, all you need is an IR light source. Heck, even a television remote control would do the trick, albeit dimly.
The problem is that cameras that are not intended as night-vision cameras have an IR filter built-in so that the camera's reaction is limited to light sources the human eye can see. And, specifically, on the external iSight, that filter is a coating that's bonded to a small block of glass inside the iSight.
Now I had a project. After first scoring a broken iSight on Craigslist, should I need parts, I took the iSight apart, took out the glass block, and removed the IR coating in a quick bath of sulfuric acid. [Do not try this at home unless you know what you are doing, please. –Ed.] You could see the film slide off the glass.
Once the iSight was reassembled and an IR light source applied, bingo! Night vision. The only downside has been that because sulfuric acid is a bit of a blunt-edged instrument (to put it mildly), whatever was giving it the ability to correctly sense the rest of the red is now gone. In the gallery, you can see the result in the last image. Ah well. If I ever want it to return to regular function, I can drop in the intact lens from the broken iSight. But for now, the increased range is a great asset. My iPhone is a little monitor that follows me around the house and pushes notification of any motion.
Special thanks to Jason Babcock, for blazing the trail on iSight tear-downs.