pinger

A device used underwater to produce pulses of sound, as for an echo sounder or a locator device.

A device that emits a short, high-pitched sound bust (i.e. goes, "ping!") such as in sonar or other echo location systems.

A device that periodically emits a signal that can be monitored to permit movement tracking.

A computer program that sends a ping message over a network.

A user of a ping program; one who pings.