In this paper, we describe LightWave, a sensing approach that turns ordinary compact fluorescent light (CFL) bulbs into sensors of human proximity. Unmodified CFL bulbs are shown to be sensitive proximity transducers when they are illuminated. This approach utilizes predictable variations in electromagnetic noise resulting from the change in impedance due to the proximity of a human body to the bulb. The electromagnetic noise can be sensed from any point along a home's electrical wiring. This allows users to perform gestures near any CFL lighting fixture, even when multiple lamps are operational. Gestures can be sensed using a single interface device plugged into any electrical outlet. We experimentally show that we can reliably detect hover gestures (waving a hand close to a lamp), touches on lampshades, and touches on the glass part of the bulb itself. Additionally, we show that touches anywhere along the body of a metal lamp can be detected. These basic detectable signals can then be combined to form complex gesture sequences for a variety of applications. We also show that CFLs can function as more general-purpose sensors for distributed human motion detection and ambient temperature sensing.