I know there are a lot of "alarm clocks" or night lights for kids available out there that do basically the same thing, but they range anywhere from $30 to $60 and with this system you have a practical lamp afterward as well.
The reason for the 20W bulb is to keep the light level down in case the child is still asleep when it turns on. If they're still sleeping they probably need it. :)
As always if you have any questions, or comments please let me know.