This home-made i2c-controlled infrared remote control can turn off the TV (or give it other commands, like lowering the volume or change channels). It is used in this robot to turn the TV off if the sound is too loud.
The most interesting aspect of this project is the use of a microcontroller in the circuit. The microcontroller listens to i2c transmissions that the NXT sends via one of the sensor ports. The transmission from the NXT contains the infrared command to send. Once such a transmission is received, the microcontroller generates the appropriate infrared signal.
The full description of the project describes how to program a low-cost microcontroller ($20 will buy both the microcontroller and the device to program it) and how to interface it to the NXT. The full description also includes a short video showing the robot actually turning of a TV with this home-made remote.