Bogdan Raducanu from Electro Bob has installed some LED Lighting that uses PIR Sensors in his kitchen and bathroom, the LED strips provide sufficient light for the areas and only turn on when someone id in the area because of the motion sensors that have been placed in strategic locations. He has documented his steps so you can also have some automatic lighting in your house.

“Tiny PIR sensors will turn on the lights in the kitchen and bathroom when someone comes in range. The sensors are rather popular modules using a BISS0001 IC; they provide a 3.3V level for an adjustable time when motion is detected. The circuit is used to turn on the hallway lights. T2 will turn off when it is dark enough, allowing T1 to turn ON and light up the LEDs. The threshold is determined by the divider formed with a photo resistor and a potentiometer. I gave up using a constant current supply in the favor of a simple current limiting resistor because at around 100mA of current (set with R3) there is no danger of thermal runaway.”