Not many people know that regular camera can be used as night vision device because it's able to take pictures in infra-red spectrum. If scenery will be lighted by source of those rays, for human eyes it will be dark, but camera will be able to take pictures.
Sensitivity to IR rays depends on many factors, from manufacturer, model. I tried with poor results SONY and Kodak cameras, but cheap mp4-player worked great. IMO it's because better equipment comes with infrared blockers.
The easiest source of infra red rays I could find was pilot remote control, but it could be also made with a couple of inexpensive IR diodes. Here are some pictures (original and computer treatment).