A novel signaling device for mounting on the rear of a bicycle that reflects and redirects light from a remote source back toward that source in the form of a pulsating or oscillating signal. It consists of a light collecting and directing means, such as a reflector or a refractive lens and a corner retro-reflector which is made to oscillate through a range of focal positions. The motion of the retro-reflector causes light from sources at any location in a particular field to periodically be reflected back to that location in a manner that produces either a pulsating signal or a signal that oscillates between separate portions of the device.