This video light takes care of this. It will come on automatically when the ambient light drops too much. A feature wich not only saves batteries but also makes for extremely easy use. You CAN set the light to always on mode (or off), but I never do.

At first I was concerned about the coverage of the light. Don't get me wrong, it is very bright but it's not going to illuminate an entire room and it shouldn't. Besides, it already sucks the batteries, any brighter and your battery life would drop to nothing. The lumination it provides is perfectly balanced for the shooting of video in low light conditions.

The final point I want to make is that this thing is TINY and it looks great mounted on the camcorder.