Record stealthily, in the dark. This hack is simple and will turn any LED flashlight into an infrared night vision light you can use with any video camera.
Infrared light is invisible to the human eye, but it will illuminate any area you are shooting. IR radiation is electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm), but shorter than a microwave (~30,000 um).
Most consumer cameras that advertise 'night vision' are equipped with IRs. Infrared light sources can be used to augment the available ambient light for conversion by night vision devices, increasing in-the-dark visibility without actually using a visible light source. The key is in the recording, the IR light is visible.
The signal is transmitted via this invisible light. Wiimotes, iPhones and weather satellites also use IR technology.
Any easy place to salvage some IRs is your television remote. It takes minor soldering to swap out the regular flashlight's LEDs with an old TV remote's IR ones.