A disposable light source device for the non-invasive visualization of veins, arteries or other subcutaneous structures of and objects in the body, or for facilitating and monitoring intravenous insertion or extraction of fluids, including a conforming layer for interfacing and optically coupling with the body surface, and adhering the device to the body portion, and a main light source for directing near infrared light through the conforming layer to illuminate the body. The disposable light source device can also include a light transmissive and electrically insulative layer that is disposed between and electrically insulates the main light source from the body-contacting conforming layer. The disposable light source device can also include a proximity sensor that controls activation of the first light source such that the light source is on only when the conforming layer is brought into proximity to the body surface.