From Gizmodo:

A device called FakeTV is intended to deter would-be burglars by making it seem like you are up watching the television when in reality you could be sleeping or out of the house. After all, burglars would rather move on to an easier target than tangle with a dangerous couch potato watching infomercials at 4 in the morning. The unit consists of a small LED lamp that gives off a light output similar to a 27-inch television. It even adds effects like scene changes, fades, swells, flicks, on-screen motion and color changes to enhance the illusion.

Obviously, if you were to leave on your actual television during the night, your electricity bill would suffer the consequences. As an alternative, the FakeTV consumes about the same amount of power as a night light and it can be set to automatically turn on at dusk and turn off at dawn. I don't know how much truth there is to the notion that burglars are less likely to attack a home with a television on, but if you can't afford an actual alarm system, spending $50 on a FakeTV unit could be an attractive option.