A signaling device, and in particular a signaling device for a striking implement such as a tennis racket, a golf club or the like, for generating signals during a movement of the signaling device (10), including a resonant body and a holding device, wherein the resonant body and the holding device are to be connected to one another or connectable to one another, so as to attach the resonant body by way of the holding device to a striking implement or the like, wherein the resonant body furthermore includes a cavity for generating an acoustic signal during a movement, wherein the resonant body has a single opening which has a fluidic operative connection to the cavity and by way of which the cavity is fluidically connected to the surrounding area.