The Canadian company Waypoint Counter Surveillance sells a Universal Exotic Modulation Detector (EMD) which claims to allow "when checking radiating fields within a room, to detect, localize and demodulate unusual technical surveillance systems including visible and non visible bulb, LED, IR, UV and laser light, ultrasonic audio transmission and induction audio transmission."

At this time of year when many of us are surrounded by an inordinate amount of LED bulbs via holiday decorations, the idea of Christmas lights spying on anyone by potentially "listening" for audio seem(s) extra creepy...