It is a light olive-green device with a light tan button, a red dial, and a light gray antennae. It is used to track sponges within a mile radius.
Role in episode
Sandy invents the tracker after SpongeBob goes to New Kelp City. However, Squidward, not wanting SpongeBob to come back, purposely destroys the device with a hammer, but claims that he dropped it, even though it is obvious that he didn't.