Lutron LRF2-OCRB-P-WH Radio Powr Savr Wireless Ceiling-Mounted Occupancy/Vacancy Sensor, White
Radio Power Saver wireless ceiling-mounted occupancy/vacancy sensors save you energy without the thought of it ever crossing your mind.  This Radio Power Saver is able to turn on the lights when you enter a room and then off after you leave it, using it's XCT passive infrared fine motion detecting technology.  This sensor is very easy to install and can control up to 10 compatible dimmers/switches.