I think there are a lot of them on the market.
I have this one:
http://www.smarthome.com/903201.html
Like other automatic night lights I have, it won't turn off in the daytime unless the room is fairly well lit. If the ambient light sensor was more sensitive, it would shut off when it saw it's own light. I have mine on a timer, but the timer cost much more than the light.
I've seen a few directional lights that may be able to turn off with less ambient light because the sensor points in a different direction than the light.
Here's one:
http://www.homedepot.com/prel80/HDUS...p?pn=100396658